refactor applypatch and friends

Change the applypatch function to take meaningful arguments instead of
argc and argv.  Move all the parsing of arguments into main.c (for the
standalone binary) and into install.c (for the updater function).
applypatch() takes patches as Value objects, so we can pass in blobs
extracted from the package without ever writing them to temp files.

The patching code is changed to read the patch from memory instead of
a file.

A bunch of compiler warnings (mostly about signed vs unsigned types)
are fixed.

Support for the IMGDIFF1 format is dropped.  (We've been generating
IMGDIFF2 packages for some time now.)

Change-Id: I217563c500012750f27110db821928a06211323f

1 files changed, 637 insertions, 722 deletions

diff --git a/applypatch/applypatch.c b/applypatch/applypatch.c
index daf3729..99d3661 100644
--- a/applypatch/applypatch.c
+++ b/applypatch/applypatch.c
@@ -28,6 +28,7 @@
 #include "mincrypt/sha.h"
 #include "applypatch.h"
 #include "mtdutils/mtdutils.h"
+#include "edify/expr.h"
 
 int SaveFileContents(const char* filename, FileContents file);
 int LoadMTDContents(const char* filename, FileContents* file);
@@ -39,57 +40,57 @@ static int mtd_partitions_scanned = 0;
 // Read a file into memory; store it and its associated metadata in
 // *file.  Return 0 on success.
 int LoadFileContents(const char* filename, FileContents* file) {
-  file->data = NULL;
+    file->data = NULL;
 
-  // A special 'filename' beginning with "MTD:" means to load the
-  // contents of an MTD partition.
-  if (strncmp(filename, "MTD:", 4) == 0) {
-    return LoadMTDContents(filename, file);
-  }
+    // A special 'filename' beginning with "MTD:" means to load the
+    // contents of an MTD partition.
+    if (strncmp(filename, "MTD:", 4) == 0) {
+        return LoadMTDContents(filename, file);
+    }
 
-  if (stat(filename, &file->st) != 0) {
-    printf("failed to stat \"%s\": %s\n", filename, strerror(errno));
-    return -1;
-  }
+    if (stat(filename, &file->st) != 0) {
+        printf("failed to stat \"%s\": %s\n", filename, strerror(errno));
+        return -1;
+    }
 
-  file->size = file->st.st_size;
-  file->data = malloc(file->size);
+    file->size = file->st.st_size;
+    file->data = malloc(file->size);
 
-  FILE* f = fopen(filename, "rb");
-  if (f == NULL) {
-    printf("failed to open \"%s\": %s\n", filename, strerror(errno));
-    free(file->data);
-    file->data = NULL;
-    return -1;
-  }
+    FILE* f = fopen(filename, "rb");
+    if (f == NULL) {
+        printf("failed to open \"%s\": %s\n", filename, strerror(errno));
+        free(file->data);
+        file->data = NULL;
+        return -1;
+    }
 
-  size_t bytes_read = fread(file->data, 1, file->size, f);
-  if (bytes_read != file->size) {
-    printf("short read of \"%s\" (%d bytes of %d)\n",
-            filename, bytes_read, file->size);
-    free(file->data);
-    file->data = NULL;
-    return -1;
-  }
-  fclose(f);
+    ssize_t bytes_read = fread(file->data, 1, file->size, f);
+    if (bytes_read != file->size) {
+        printf("short read of \"%s\" (%ld bytes of %ld)\n",
+               filename, (long)bytes_read, (long)file->size);
+        free(file->data);
+        file->data = NULL;
+        return -1;
+    }
+    fclose(f);
 
-  SHA(file->data, file->size, file->sha1);
-  return 0;
+    SHA(file->data, file->size, file->sha1);
+    return 0;
 }
 
 static size_t* size_array;
 // comparison function for qsort()ing an int array of indexes into
 // size_array[].
 static int compare_size_indices(const void* a, const void* b) {
-  int aa = *(int*)a;
-  int bb = *(int*)b;
-  if (size_array[aa] < size_array[bb]) {
-    return -1;
-  } else if (size_array[aa] > size_array[bb]) {
-    return 1;
-  } else {
-    return 0;
-  }
+    int aa = *(int*)a;
+    int bb = *(int*)b;
+    if (size_array[aa] < size_array[bb]) {
+        return -1;
+    } else if (size_array[aa] > size_array[bb]) {
+        return 1;
+    } else {
+        return 0;
+    }
 }
 
 void FreeFileContents(FileContents* file) {
@@ -113,239 +114,240 @@ void FreeFileContents(FileContents* file) {
 // hash of the data, and we'll do the load expecting to find one of
 // those hashes.
 int LoadMTDContents(const char* filename, FileContents* file) {
-  char* copy = strdup(filename);
-  const char* magic = strtok(copy, ":");
-  if (strcmp(magic, "MTD") != 0) {
-    printf("LoadMTDContents called with bad filename (%s)\n",
-            filename);
-    return -1;
-  }
-  const char* partition = strtok(NULL, ":");
-
-  int i;
-  int colons = 0;
-  for (i = 0; filename[i] != '\0'; ++i) {
-    if (filename[i] == ':') {
-      ++colons;
-    }
-  }
-  if (colons < 3 || colons%2 == 0) {
-    printf("LoadMTDContents called with bad filename (%s)\n",
-            filename);
-  }
-
-  int pairs = (colons-1)/2;     // # of (size,sha1) pairs in filename
-  int* index = malloc(pairs * sizeof(int));
-  size_t* size = malloc(pairs * sizeof(size_t));
-  char** sha1sum = malloc(pairs * sizeof(char*));
-
-  for (i = 0; i < pairs; ++i) {
-    const char* size_str = strtok(NULL, ":");
-    size[i] = strtol(size_str, NULL, 10);
-    if (size[i] == 0) {
-      printf("LoadMTDContents called with bad size (%s)\n", filename);
-      return -1;
-    }
-    sha1sum[i] = strtok(NULL, ":");
-    index[i] = i;
-  }
-
-  // sort the index[] array so it indexes the pairs in order of
-  // increasing size.
-  size_array = size;
-  qsort(index, pairs, sizeof(int), compare_size_indices);
-
-  if (!mtd_partitions_scanned) {
-    mtd_scan_partitions();
-    mtd_partitions_scanned = 1;
-  }
-
-  const MtdPartition* mtd = mtd_find_partition_by_name(partition);
-  if (mtd == NULL) {
-    printf("mtd partition \"%s\" not found (loading %s)\n",
-            partition, filename);
-    return -1;
-  }
-
-  MtdReadContext* ctx = mtd_read_partition(mtd);
-  if (ctx == NULL) {
-    printf("failed to initialize read of mtd partition \"%s\"\n",
-            partition);
-    return -1;
-  }
-
-  SHA_CTX sha_ctx;
-  SHA_init(&sha_ctx);
-  uint8_t parsed_sha[SHA_DIGEST_SIZE];
-
-  // allocate enough memory to hold the largest size.
-  file->data = malloc(size[index[pairs-1]]);
-  char* p = (char*)file->data;
-  file->size = 0;                // # bytes read so far
-
-  for (i = 0; i < pairs; ++i) {
-    // Read enough additional bytes to get us up to the next size
-    // (again, we're trying the possibilities in order of increasing
-    // size).
-    size_t next = size[index[i]] - file->size;
-    size_t read = 0;
-    if (next > 0) {
-      read = mtd_read_data(ctx, p, next);
-      if (next != read) {
-        printf("short read (%d bytes of %d) for partition \"%s\"\n",
-                read, next, partition);
-        free(file->data);
-        file->data = NULL;
+    char* copy = strdup(filename);
+    const char* magic = strtok(copy, ":");
+    if (strcmp(magic, "MTD") != 0) {
+        printf("LoadMTDContents called with bad filename (%s)\n",
+               filename);
         return -1;
-      }
-      SHA_update(&sha_ctx, p, read);
-      file->size += read;
     }
+    const char* partition = strtok(NULL, ":");
 
-    // Duplicate the SHA context and finalize the duplicate so we can
-    // check it against this pair's expected hash.
-    SHA_CTX temp_ctx;
-    memcpy(&temp_ctx, &sha_ctx, sizeof(SHA_CTX));
-    const uint8_t* sha_so_far = SHA_final(&temp_ctx);
+    int i;
+    int colons = 0;
+    for (i = 0; filename[i] != '\0'; ++i) {
+        if (filename[i] == ':') {
+            ++colons;
+        }
+    }
+    if (colons < 3 || colons%2 == 0) {
+        printf("LoadMTDContents called with bad filename (%s)\n",
+               filename);
+    }
 
-    if (ParseSha1(sha1sum[index[i]], parsed_sha) != 0) {
-      printf("failed to parse sha1 %s in %s\n",
-              sha1sum[index[i]], filename);
-      free(file->data);
-      file->data = NULL;
-      return -1;
+    int pairs = (colons-1)/2;     // # of (size,sha1) pairs in filename
+    int* index = malloc(pairs * sizeof(int));
+    size_t* size = malloc(pairs * sizeof(size_t));
+    char** sha1sum = malloc(pairs * sizeof(char*));
+
+    for (i = 0; i < pairs; ++i) {
+        const char* size_str = strtok(NULL, ":");
+        size[i] = strtol(size_str, NULL, 10);
+        if (size[i] == 0) {
+            printf("LoadMTDContents called with bad size (%s)\n", filename);
+            return -1;
+        }
+        sha1sum[i] = strtok(NULL, ":");
+        index[i] = i;
     }
 
-    if (memcmp(sha_so_far, parsed_sha, SHA_DIGEST_SIZE) == 0) {
-      // we have a match.  stop reading the partition; we'll return
-      // the data we've read so far.
-      printf("mtd read matched size %d sha %s\n",
-             size[index[i]], sha1sum[index[i]]);
-      break;
+    // sort the index[] array so it indexes the pairs in order of
+    // increasing size.
+    size_array = size;
+    qsort(index, pairs, sizeof(int), compare_size_indices);
+
+    if (!mtd_partitions_scanned) {
+        mtd_scan_partitions();
+        mtd_partitions_scanned = 1;
     }
 
-    p += read;
-  }
+    const MtdPartition* mtd = mtd_find_partition_by_name(partition);
+    if (mtd == NULL) {
+        printf("mtd partition \"%s\" not found (loading %s)\n",
+               partition, filename);
+        return -1;
+    }
 
-  mtd_read_close(ctx);
+    MtdReadContext* ctx = mtd_read_partition(mtd);
+    if (ctx == NULL) {
+        printf("failed to initialize read of mtd partition \"%s\"\n",
+               partition);
+        return -1;
+    }
 
-  if (i == pairs) {
-    // Ran off the end of the list of (size,sha1) pairs without
-    // finding a match.
-    printf("contents of MTD partition \"%s\" didn't match %s\n",
-            partition, filename);
-    free(file->data);
-    file->data = NULL;
-    return -1;
-  }
+    SHA_CTX sha_ctx;
+    SHA_init(&sha_ctx);
+    uint8_t parsed_sha[SHA_DIGEST_SIZE];
+
+    // allocate enough memory to hold the largest size.
+    file->data = malloc(size[index[pairs-1]]);
+    char* p = (char*)file->data;
+    file->size = 0;                // # bytes read so far
+
+    for (i = 0; i < pairs; ++i) {
+        // Read enough additional bytes to get us up to the next size
+        // (again, we're trying the possibilities in order of increasing
+        // size).
+        size_t next = size[index[i]] - file->size;
+        size_t read = 0;
+        if (next > 0) {
+            read = mtd_read_data(ctx, p, next);
+            if (next != read) {
+                printf("short read (%d bytes of %d) for partition \"%s\"\n",
+                       read, next, partition);
+                free(file->data);
+                file->data = NULL;
+                return -1;
+            }
+            SHA_update(&sha_ctx, p, read);
+            file->size += read;
+        }
+
+        // Duplicate the SHA context and finalize the duplicate so we can
+        // check it against this pair's expected hash.
+        SHA_CTX temp_ctx;
+        memcpy(&temp_ctx, &sha_ctx, sizeof(SHA_CTX));
+        const uint8_t* sha_so_far = SHA_final(&temp_ctx);
+
+        if (ParseSha1(sha1sum[index[i]], parsed_sha) != 0) {
+            printf("failed to parse sha1 %s in %s\n",
+                   sha1sum[index[i]], filename);
+            free(file->data);
+            file->data = NULL;
+            return -1;
+        }
+
+        if (memcmp(sha_so_far, parsed_sha, SHA_DIGEST_SIZE) == 0) {
+            // we have a match.  stop reading the partition; we'll return
+            // the data we've read so far.
+            printf("mtd read matched size %d sha %s\n",
+                   size[index[i]], sha1sum[index[i]]);
+            break;
+        }
 
-  const uint8_t* sha_final = SHA_final(&sha_ctx);
-  for (i = 0; i < SHA_DIGEST_SIZE; ++i) {
-    file->sha1[i] = sha_final[i];
-  }
+        p += read;
+    }
+
+    mtd_read_close(ctx);
+
+    if (i == pairs) {
+        // Ran off the end of the list of (size,sha1) pairs without
+        // finding a match.
+        printf("contents of MTD partition \"%s\" didn't match %s\n",
+               partition, filename);
+        free(file->data);
+        file->data = NULL;
+        return -1;
+    }
+
+    const uint8_t* sha_final = SHA_final(&sha_ctx);
+    for (i = 0; i < SHA_DIGEST_SIZE; ++i) {
+        file->sha1[i] = sha_final[i];
+    }
 
-  // Fake some stat() info.
-  file->st.st_mode = 0644;
-  file->st.st_uid = 0;
-  file->st.st_gid = 0;
+    // Fake some stat() info.
+    file->st.st_mode = 0644;
+    file->st.st_uid = 0;
+    file->st.st_gid = 0;
 
-  free(copy);
-  free(index);
-  free(size);
-  free(sha1sum);
+    free(copy);
+    free(index);
+    free(size);
+    free(sha1sum);
 
-  return 0;
+    return 0;
 }
 
 
 // Save the contents of the given FileContents object under the given
 // filename.  Return 0 on success.
 int SaveFileContents(const char* filename, FileContents file) {
-  int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC);
-  if (fd < 0) {
-    printf("failed to open \"%s\" for write: %s\n",
-            filename, strerror(errno));
-    return -1;
-  }
+    int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC);
+    if (fd < 0) {
+        printf("failed to open \"%s\" for write: %s\n",
+               filename, strerror(errno));
+        return -1;
+    }
 
-  size_t bytes_written = FileSink(file.data, file.size, &fd);
-  if (bytes_written != file.size) {
-    printf("short write of \"%s\" (%d bytes of %d) (%s)\n",
-           filename, bytes_written, file.size, strerror(errno));
+    ssize_t bytes_written = FileSink(file.data, file.size, &fd);
+    if (bytes_written != file.size) {
+        printf("short write of \"%s\" (%ld bytes of %ld) (%s)\n",
+               filename, (long)bytes_written, (long)file.size,
+               strerror(errno));
+        close(fd);
+        return -1;
+    }
+    fsync(fd);
     close(fd);
-    return -1;
-  }
-  fsync(fd);
-  close(fd);
 
-  if (chmod(filename, file.st.st_mode) != 0) {
-    printf("chmod of \"%s\" failed: %s\n", filename, strerror(errno));
-    return -1;
-  }
-  if (chown(filename, file.st.st_uid, file.st.st_gid) != 0) {
-    printf("chown of \"%s\" failed: %s\n", filename, strerror(errno));
-    return -1;
-  }
+    if (chmod(filename, file.st.st_mode) != 0) {
+        printf("chmod of \"%s\" failed: %s\n", filename, strerror(errno));
+        return -1;
+    }
+    if (chown(filename, file.st.st_uid, file.st.st_gid) != 0) {
+        printf("chown of \"%s\" failed: %s\n", filename, strerror(errno));
+        return -1;
+    }
 
-  return 0;
+    return 0;
 }
 
 // Write a memory buffer to target_mtd partition, a string of the form
 // "MTD:<partition>[:...]".  Return 0 on success.
 int WriteToMTDPartition(unsigned char* data, size_t len,
                         const char* target_mtd) {
-  char* partition = strchr(target_mtd, ':');
-  if (partition == NULL) {
-    printf("bad MTD target name \"%s\"\n", target_mtd);
-    return -1;
-  }
-  ++partition;
-  // Trim off anything after a colon, eg "MTD:boot:blah:blah:blah...".
-  // We want just the partition name "boot".
-  partition = strdup(partition);
-  char* end = strchr(partition, ':');
-  if (end != NULL)
-    *end = '\0';
-
-  if (!mtd_partitions_scanned) {
-    mtd_scan_partitions();
-    mtd_partitions_scanned = 1;
-  }
-
-  const MtdPartition* mtd = mtd_find_partition_by_name(partition);
-  if (mtd == NULL) {
-    printf("mtd partition \"%s\" not found for writing\n", partition);
-    return -1;
-  }
+    char* partition = strchr(target_mtd, ':');
+    if (partition == NULL) {
+        printf("bad MTD target name \"%s\"\n", target_mtd);
+        return -1;
+    }
+    ++partition;
+    // Trim off anything after a colon, eg "MTD:boot:blah:blah:blah...".
+    // We want just the partition name "boot".
+    partition = strdup(partition);
+    char* end = strchr(partition, ':');
+    if (end != NULL)
+        *end = '\0';
+
+    if (!mtd_partitions_scanned) {
+        mtd_scan_partitions();
+        mtd_partitions_scanned = 1;
+    }
 
-  MtdWriteContext* ctx = mtd_write_partition(mtd);
-  if (ctx == NULL) {
-    printf("failed to init mtd partition \"%s\" for writing\n",
-            partition);
-    return -1;
-  }
+    const MtdPartition* mtd = mtd_find_partition_by_name(partition);
+    if (mtd == NULL) {
+        printf("mtd partition \"%s\" not found for writing\n", partition);
+        return -1;
+    }
 
-  size_t written = mtd_write_data(ctx, (char*)data, len);
-  if (written != len) {
-    printf("only wrote %d of %d bytes to MTD %s\n",
-            written, len, partition);
-    mtd_write_close(ctx);
-    return -1;
-  }
+    MtdWriteContext* ctx = mtd_write_partition(mtd);
+    if (ctx == NULL) {
+        printf("failed to init mtd partition \"%s\" for writing\n",
+               partition);
+        return -1;
+    }
 
-  if (mtd_erase_blocks(ctx, -1) < 0) {
-    printf("error finishing mtd write of %s\n", partition);
-    mtd_write_close(ctx);
-    return -1;
-  }
+    size_t written = mtd_write_data(ctx, (char*)data, len);
+    if (written != len) {
+        printf("only wrote %d of %d bytes to MTD %s\n",
+               written, len, partition);
+        mtd_write_close(ctx);
+        return -1;
+    }
 
-  if (mtd_write_close(ctx)) {
-    printf("error closing mtd write of %s\n", partition);
-    return -1;
-  }
+    if (mtd_erase_blocks(ctx, -1) < 0) {
+        printf("error finishing mtd write of %s\n", partition);
+        mtd_write_close(ctx);
+        return -1;
+    }
 
-  free(partition);
-  return 0;
+    if (mtd_write_close(ctx)) {
+        printf("error closing mtd write of %s\n", partition);
+        return -1;
+    }
+
+    free(partition);
+    return 0;
 }
 
 
@@ -354,547 +356,460 @@ int WriteToMTDPartition(unsigned char* data, size_t len,
 // the form "<digest>:<anything>".  Return 0 on success, -1 on any
 // error.
 int ParseSha1(const char* str, uint8_t* digest) {
-  int i;
-  const char* ps = str;
-  uint8_t* pd = digest;
-  for (i = 0; i < SHA_DIGEST_SIZE * 2; ++i, ++ps) {
-    int digit;
-    if (*ps >= '0' && *ps <= '9') {
-      digit = *ps - '0';
-    } else if (*ps >= 'a' && *ps <= 'f') {
-      digit = *ps - 'a' + 10;
-    } else if (*ps >= 'A' && *ps <= 'F') {
-      digit = *ps - 'A' + 10;
-    } else {
-      return -1;
-    }
-    if (i % 2 == 0) {
-      *pd = digit << 4;
-    } else {
-      *pd |= digit;
-      ++pd;
-    }
-  }
-  if (*ps != '\0' && *ps != ':') return -1;
-  return 0;
-}
-
-// Parse arguments (which should be of the form "<sha1>" or
-// "<sha1>:<filename>" into the array *patches, returning the number
-// of Patch objects in *num_patches.  Return 0 on success.
-int ParseShaArgs(int argc, char** argv, Patch** patches, int* num_patches) {
-  *num_patches = argc;
-  *patches = malloc(*num_patches * sizeof(Patch));
-
-  int i;
-  for (i = 0; i < *num_patches; ++i) {
-    if (ParseSha1(argv[i], (*patches)[i].sha1) != 0) {
-      printf("failed to parse sha1 \"%s\"\n", argv[i]);
-      return -1;
-    }
-    if (argv[i][SHA_DIGEST_SIZE*2] == '\0') {
-      (*patches)[i].patch_filename = NULL;
-    } else if (argv[i][SHA_DIGEST_SIZE*2] == ':') {
-      (*patches)[i].patch_filename = argv[i] + (SHA_DIGEST_SIZE*2+1);
-    } else {
-      printf("failed to parse filename \"%s\"\n", argv[i]);
-      return -1;
+    int i;
+    const char* ps = str;
+    uint8_t* pd = digest;
+    for (i = 0; i < SHA_DIGEST_SIZE * 2; ++i, ++ps) {
+        int digit;
+        if (*ps >= '0' && *ps <= '9') {
+            digit = *ps - '0';
+        } else if (*ps >= 'a' && *ps <= 'f') {
+            digit = *ps - 'a' + 10;
+        } else if (*ps >= 'A' && *ps <= 'F') {
+            digit = *ps - 'A' + 10;
+        } else {
+            return -1;
+        }
+        if (i % 2 == 0) {
+            *pd = digit << 4;
+        } else {
+            *pd |= digit;
+            ++pd;
+        }
     }
-  }
-
-  return 0;
+    if (*ps != '\0') return -1;
+    return 0;
 }
 
-// Search an array of Patch objects for one matching the given sha1.
-// Return the Patch object on success, or NULL if no match is found.
-const Patch* FindMatchingPatch(uint8_t* sha1, Patch* patches, int num_patches) {
-  int i;
-  for (i = 0; i < num_patches; ++i) {
-    if (memcmp(patches[i].sha1, sha1, SHA_DIGEST_SIZE) == 0) {
-      return patches+i;
+// Search an array of sha1 strings for one matching the given sha1.
+// Return the index of the match on success, or -1 if no match is
+// found.
+int FindMatchingPatch(uint8_t* sha1, char** const patch_sha1_str,
+                      int num_patches) {
+    int i;
+    uint8_t patch_sha1[SHA_DIGEST_SIZE];
+    for (i = 0; i < num_patches; ++i) {
+        if (ParseSha1(patch_sha1_str[i], patch_sha1) == 0 &&
+            memcmp(patch_sha1, sha1, SHA_DIGEST_SIZE) == 0) {
+            return i;
+        }
     }
-  }
-  return NULL;
+    return -1;
 }
 
 // Returns 0 if the contents of the file (argv[2]) or the cached file
 // match any of the sha1's on the command line (argv[3:]).  Returns
 // nonzero otherwise.
-int CheckMode(int argc, char** argv) {
-  if (argc < 3) {
-    printf("no filename given\n");
-    return 2;
-  }
-
-  int num_patches;
-  Patch* patches;
-  if (ParseShaArgs(argc-3, argv+3, &patches, &num_patches) != 0) { return 1; }
-
-  FileContents file;
-  file.data = NULL;
-
-  // It's okay to specify no sha1s; the check will pass if the
-  // LoadFileContents is successful.  (Useful for reading MTD
-  // partitions, where the filename encodes the sha1s; no need to
-  // check them twice.)
-  if (LoadFileContents(argv[2], &file) != 0 ||
-      (num_patches > 0 &&
-       FindMatchingPatch(file.sha1, patches, num_patches) == NULL)) {
-    printf("file \"%s\" doesn't have any of expected "
-            "sha1 sums; checking cache\n", argv[2]);
-
-    free(file.data);
-
-    // If the source file is missing or corrupted, it might be because
-    // we were killed in the middle of patching it.  A copy of it
-    // should have been made in CACHE_TEMP_SOURCE.  If that file
-    // exists and matches the sha1 we're looking for, the check still
-    // passes.
-
-    if (LoadFileContents(CACHE_TEMP_SOURCE, &file) != 0) {
-      printf("failed to load cache file\n");
-      return 1;
-    }
+int applypatch_check(const char* filename,
+                     int num_patches, char** const patch_sha1_str) {
+    FileContents file;
+    file.data = NULL;
+
+    // It's okay to specify no sha1s; the check will pass if the
+    // LoadFileContents is successful.  (Useful for reading MTD
+    // partitions, where the filename encodes the sha1s; no need to
+    // check them twice.)
+    if (LoadFileContents(filename, &file) != 0 ||
+        (num_patches > 0 &&
+         FindMatchingPatch(file.sha1, patch_sha1_str, num_patches) < 0)) {
+        printf("file \"%s\" doesn't have any of expected "
+               "sha1 sums; checking cache\n", filename);
+
+        free(file.data);
+
+        // If the source file is missing or corrupted, it might be because
+        // we were killed in the middle of patching it.  A copy of it
+        // should have been made in CACHE_TEMP_SOURCE.  If that file
+        // exists and matches the sha1 we're looking for, the check still
+        // passes.
+
+        if (LoadFileContents(CACHE_TEMP_SOURCE, &file) != 0) {
+            printf("failed to load cache file\n");
+            return 1;
+        }
 
-    if (FindMatchingPatch(file.sha1, patches, num_patches) == NULL) {
-      printf("cache bits don't match any sha1 for \"%s\"\n",
-              argv[2]);
-      return 1;
+        if (FindMatchingPatch(file.sha1, patch_sha1_str, num_patches) < 0) {
+            printf("cache bits don't match any sha1 for \"%s\"\n", filename);
+            free(file.data);
+            return 1;
+        }
     }
-  }
 
-  free(file.data);
-  return 0;
+    free(file.data);
+    return 0;
 }
 
 int ShowLicenses() {
-  ShowBSDiffLicense();
-  return 0;
+    ShowBSDiffLicense();
+    return 0;
 }
 
 ssize_t FileSink(unsigned char* data, ssize_t len, void* token) {
-  int fd = *(int *)token;
-  ssize_t done = 0;
-  ssize_t wrote;
-  while (done < (ssize_t) len) {
-    wrote = write(fd, data+done, len-done);
-    if (wrote <= 0) {
-      printf("error writing %d bytes: %s\n", (int)(len-done), strerror(errno));
-      return done;
-    }
-    done += wrote;
-  }
-  printf("wrote %d bytes to output\n", (int)done);
-  return done;
+    int fd = *(int *)token;
+    ssize_t done = 0;
+    ssize_t wrote;
+    while (done < (ssize_t) len) {
+        wrote = write(fd, data+done, len-done);
+        if (wrote <= 0) {
+            printf("error writing %d bytes: %s\n", (int)(len-done), strerror(errno));
+            return done;
+        }
+        done += wrote;
+    }
+    return done;
 }
 
 typedef struct {
-  unsigned char* buffer;
-  ssize_t size;
-  ssize_t pos;
+    unsigned char* buffer;
+    ssize_t size;
+    ssize_t pos;
 } MemorySinkInfo;
 
 ssize_t MemorySink(unsigned char* data, ssize_t len, void* token) {
-  MemorySinkInfo* msi = (MemorySinkInfo*)token;
-  if (msi->size - msi->pos < len) {
-    return -1;
-  }
-  memcpy(msi->buffer + msi->pos, data, len);
-  msi->pos += len;
-  return len;
+    MemorySinkInfo* msi = (MemorySinkInfo*)token;
+    if (msi->size - msi->pos < len) {
+        return -1;
+    }
+    memcpy(msi->buffer + msi->pos, data, len);
+    msi->pos += len;
+    return len;
 }
 
 // Return the amount of free space (in bytes) on the filesystem
 // containing filename.  filename must exist.  Return -1 on error.
 size_t FreeSpaceForFile(const char* filename) {
-  struct statfs sf;
-  if (statfs(filename, &sf) != 0) {
-    printf("failed to statfs %s: %s\n", filename, strerror(errno));
-    return -1;
-  }
-  return sf.f_bsize * sf.f_bfree;
+    struct statfs sf;
+    if (statfs(filename, &sf) != 0) {
+        printf("failed to statfs %s: %s\n", filename, strerror(errno));
+        return -1;
+    }
+    return sf.f_bsize * sf.f_bfree;
+}
+
+int CacheSizeCheck(size_t bytes) {
+    if (MakeFreeSpaceOnCache(bytes) < 0) {
+        printf("unable to make %ld bytes available on /cache\n", (long)bytes);
+        return 1;
+    } else {
+        return 0;
+    }
 }
 
-// This program applies binary patches to files in a way that is safe
+
+// This function applies binary patches to files in a way that is safe
 // (the original file is not touched until we have the desired
 // replacement for it) and idempotent (it's okay to run this program
 // multiple times).
 //
-// - if the sha1 hash of <tgt-file> is <tgt-sha1>, does nothing and exits
-//   successfully.
+// - if the sha1 hash of <target_filename> is <target_sha1_string>,
+//   does nothing and exits successfully.
 //
-// - otherwise, if the sha1 hash of <src-file> is <src-sha1>, applies the
-//   bsdiff <patch> to <src-file> to produce a new file (the type of patch
-//   is automatically detected from the file header).  If that new
-//   file has sha1 hash <tgt-sha1>, moves it to replace <tgt-file>, and
-//   exits successfully.  Note that if <src-file> and <tgt-file> are
-//   not the same, <src-file> is NOT deleted on success.  <tgt-file>
-//   may be the string "-" to mean "the same as src-file".
+// - otherwise, if the sha1 hash of <source_filename> is one of the
+//   entries in <patch_sha1_str>, the corresponding patch from
+//   <patch_data> (which must be a VAL_BLOB) is applied to produce a
+//   new file (the type of patch is automatically detected from the
+//   blob daat).  If that new file has sha1 hash <target_sha1_str>,
+//   moves it to replace <target_filename>, and exits successfully.
+//   Note that if <source_filename> and <target_filename> are not the
+//   same, <source_filename> is NOT deleted on success.
+//   <target_filename> may be the string "-" to mean "the same as
+//   source_filename".
 //
 // - otherwise, or if any error is encountered, exits with non-zero
 //   status.
 //
-// <src-file> (or <file> in check mode) may refer to an MTD partition
-// to read the source data.  See the comments for the
-// LoadMTDContents() function above for the format of such a filename.
-//
-//
-// As you might guess from the arguments, this function used to be
-// main(); it was split out this way so applypatch could be built as a
-// static library and linked into other executables as well.  In the
-// future only the library form will exist; we will not need to build
-// this as a standalone executable.
-//
-// The arguments to this function are just the command-line of the
-// standalone executable:
-//
-// <src-file> <tgt-file> <tgt-sha1> <tgt-size> [<src-sha1>:<patch> ...]
-//    to apply a patch.  Returns 0 on success, 1 on failure.
-//
-// "-c" <file> [<sha1> ...]
-//    to check a file's contents against zero or more sha1s.  Returns
-//    0 if it matches any of them, 1 if it doesn't.
-//
-// "-s" <bytes>
-//    returns 0 if enough free space is available on /cache; 1 if it
-//    does not.
-//
-// "-l"
-//    shows open-source license information and returns 0.
-//
-// This function returns 2 if the arguments are not understood (in the
-// standalone executable, this causes the usage message to be
-// printed).
-//
-// TODO: make the interface more sensible for use as a library.
-
-int applypatch(int argc, char** argv) {
-  if (argc < 2) {
-    return 2;
-  }
+// <source_filename> may refer to an MTD partition to read the source
+// data.  See the comments for the LoadMTDContents() function above
+// for the format of such a filename.
+
+int applypatch(const char* source_filename,
+               const char* target_filename,
+               const char* target_sha1_str,
+               size_t target_size,
+               int num_patches,
+               char** const patch_sha1_str,
+               Value** patch_data) {
+    printf("\napplying patch to %s\n", source_filename);
+
+    if (target_filename[0] == '-' &&
+        target_filename[1] == '\0') {
+        target_filename = source_filename;
+    }
 
-  if (strncmp(argv[1], "-l", 3) == 0) {
-    return ShowLicenses();
-  }
+    uint8_t target_sha1[SHA_DIGEST_SIZE];
+    if (ParseSha1(target_sha1_str, target_sha1) != 0) {
+        printf("failed to parse tgt-sha1 \"%s\"\n", target_sha1_str);
+        return 1;
+    }
 
-  if (strncmp(argv[1], "-c", 3) == 0) {
-    return CheckMode(argc, argv);
-  }
+    FileContents copy_file;
+    FileContents source_file;
+    const Value* source_patch_value = NULL;
+    const Value* copy_patch_value = NULL;
+    int made_copy = 0;
+
+    // We try to load the target file into the source_file object.
+    if (LoadFileContents(target_filename, &source_file) == 0) {
+        if (memcmp(source_file.sha1, target_sha1, SHA_DIGEST_SIZE) == 0) {
+            // The early-exit case:  the patch was already applied, this file
+            // has the desired hash, nothing for us to do.
+            printf("\"%s\" is already target; no patch needed\n",
+                   target_filename);
+            return 0;
+        }
+    }
 
-  if (strncmp(argv[1], "-s", 3) == 0) {
-    if (argc != 3) {
-      return 2;
+    if (source_file.data == NULL ||
+        (target_filename != source_filename &&
+         strcmp(target_filename, source_filename) != 0)) {
+        // Need to load the source file:  either we failed to load the
+        // target file, or we did but it's different from the source file.
+        free(source_file.data);
+        LoadFileContents(source_filename, &source_file);
     }
-    size_t bytes = strtol(argv[2], NULL, 10);
-    if (MakeFreeSpaceOnCache(bytes) < 0) {
-      printf("unable to make %ld bytes available on /cache\n", (long)bytes);
-      return 1;
-    } else {
-      return 0;
-    }
-  }
-
-  uint8_t target_sha1[SHA_DIGEST_SIZE];
-
-  const char* source_filename = argv[1];
-  const char* target_filename = argv[2];
-  if (target_filename[0] == '-' &&
-      target_filename[1] == '\0') {
-    target_filename = source_filename;
-  }
-
-  printf("\napplying patch to %s\n", source_filename);
-
-  if (ParseSha1(argv[3], target_sha1) != 0) {
-    printf("failed to parse tgt-sha1 \"%s\"\n", argv[3]);
-    return 1;
-  }
-
-  unsigned long target_size = strtoul(argv[4], NULL, 0);
-
-  int num_patches;
-  Patch* patches;
-  if (ParseShaArgs(argc-5, argv+5, &patches, &num_patches) < 0) { return 1; }
-
-  FileContents copy_file;
-  FileContents source_file;
-  const char* source_patch_filename = NULL;
-  const char* copy_patch_filename = NULL;
-  int made_copy = 0;
-
-  // We try to load the target file into the source_file object.
-  if (LoadFileContents(target_filename, &source_file) == 0) {
-    if (memcmp(source_file.sha1, target_sha1, SHA_DIGEST_SIZE) == 0) {
-      // The early-exit case:  the patch was already applied, this file
-      // has the desired hash, nothing for us to do.
-      printf("\"%s\" is already target; no patch needed\n",
-              target_filename);
-      return 0;
-    }
-  }
-
-  if (source_file.data == NULL ||
-      (target_filename != source_filename &&
-       strcmp(target_filename, source_filename) != 0)) {
-    // Need to load the source file:  either we failed to load the
-    // target file, or we did but it's different from the source file.
-    free(source_file.data);
-    LoadFileContents(source_filename, &source_file);
-  }
-
-  if (source_file.data != NULL) {
-    const Patch* to_use =
-        FindMatchingPatch(source_file.sha1, patches, num_patches);
-    if (to_use != NULL) {
-      source_patch_filename = to_use->patch_filename;
-    }
-  }
-
-  if (source_patch_filename == NULL) {
-    free(source_file.data);
-    printf("source file is bad; trying copy\n");
-
-    if (LoadFileContents(CACHE_TEMP_SOURCE, &copy_file) < 0) {
-      // fail.
-      printf("failed to read copy file\n");
-      return 1;
-    }
-
-    const Patch* to_use =
-        FindMatchingPatch(copy_file.sha1, patches, num_patches);
-    if (to_use != NULL) {
-      copy_patch_filename = to_use->patch_filename;
-    }
-
-    if (copy_patch_filename == NULL) {
-      // fail.
-      printf("copy file doesn't match source SHA-1s either\n");
-      return 1;
-    }
-  }
-
-  int retry = 1;
-  SHA_CTX ctx;
-  int output;
-  MemorySinkInfo msi;
-  FileContents* source_to_use;
-  char* outname;
-
-  // assume that target_filename (eg "/system/app/Foo.apk") is located
-  // on the same filesystem as its top-level directory ("/system").
-  // We need something that exists for calling statfs().
-  char target_fs[strlen(target_filename)+1];
-  char* slash = strchr(target_filename+1, '/');
-  if (slash != NULL) {
-    int count = slash - target_filename;
-    strncpy(target_fs, target_filename, count);
-    target_fs[count] = '\0';
-  } else {
-    strcpy(target_fs, target_filename);
-  }
-
-  do {
-    // Is there enough room in the target filesystem to hold the patched
-    // file?
-
-    if (strncmp(target_filename, "MTD:", 4) == 0) {
-      // If the target is an MTD partition, we're actually going to
-      // write the output to /tmp and then copy it to the partition.
-      // statfs() always returns 0 blocks free for /tmp, so instead
-      // we'll just assume that /tmp has enough space to hold the file.
-
-      // We still write the original source to cache, in case the MTD
-      // write is interrupted.
-      if (MakeFreeSpaceOnCache(source_file.size) < 0) {
-        printf("not enough free space on /cache\n");
-        return 1;
-      }
-      if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
-        printf("failed to back up source file\n");
-        return 1;
-      }
-      made_copy = 1;
-      retry = 0;
-    } else {
-      int enough_space = 0;
-      if (retry > 0) {
-        size_t free_space = FreeSpaceForFile(target_fs);
-        int enough_space =
-          (free_space > (target_size * 3 / 2));  // 50% margin of error
-        printf("target %ld bytes; free space %ld bytes; retry %d; enough %d\n",
-               (long)target_size, (long)free_space, retry, enough_space);
-      }
-
-      if (!enough_space) {
-        retry = 0;
-      }
-
-      if (!enough_space && source_patch_filename != NULL) {
-        // Using the original source, but not enough free space.  First
-        // copy the source file to cache, then delete it from the original
-        // location.
-
-        if (strncmp(source_filename, "MTD:", 4) == 0) {
-          // It's impossible to free space on the target filesystem by
-          // deleting the source if the source is an MTD partition.  If
-          // we're ever in a state where we need to do this, fail.
-          printf("not enough free space for target but source is MTD\n");
-          return 1;
+
+    if (source_file.data != NULL) {
+        int to_use = FindMatchingPatch(source_file.sha1,
+                                       patch_sha1_str, num_patches);
+        if (to_use >= 0) {
+            source_patch_value = patch_data[to_use];
         }
+    }
 
-        if (MakeFreeSpaceOnCache(source_file.size) < 0) {
-          printf("not enough free space on /cache\n");
-          return 1;
+    if (source_patch_value == NULL) {
+        free(source_file.data);
+        printf("source file is bad; trying copy\n");
+
+        if (LoadFileContents(CACHE_TEMP_SOURCE, &copy_file) < 0) {
+            // fail.
+            printf("failed to read copy file\n");
+            return 1;
         }
 
-        if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
-          printf("failed to back up source file\n");
-          return 1;
+        int to_use = FindMatchingPatch(copy_file.sha1,
+                                       patch_sha1_str, num_patches);
+        if (to_use > 0) {
+            copy_patch_value = patch_data[to_use];
         }
-        made_copy = 1;
-        unlink(source_filename);
 
-        size_t free_space = FreeSpaceForFile(target_fs);
-        printf("(now %ld bytes free for target)\n", (long)free_space);
-      }
+        if (copy_patch_value == NULL) {
+            // fail.
+            printf("copy file doesn't match source SHA-1s either\n");
+            return 1;
+        }
     }
 
-    const char* patch_filename;
-    if (source_patch_filename != NULL) {
-      source_to_use = &source_file;
-      patch_filename = source_patch_filename;
-    } else {
-      source_to_use = &copy_file;
-      patch_filename = copy_patch_filename;
-    }
-
-    SinkFn sink = NULL;
-    void* token = NULL;
-    output = -1;
-    outname = NULL;
-    if (strncmp(target_filename, "MTD:", 4) == 0) {
-      // We store the decoded output in memory.
-      msi.buffer = malloc(target_size);
-      if (msi.buffer == NULL) {
-        printf("failed to alloc %ld bytes for output\n",
-               (long)target_size);
-        return 1;
-      }
-      msi.pos = 0;
-      msi.size = target_size;
-      sink = MemorySink;
-      token = &msi;
-    } else {
-      // We write the decoded output to "<tgt-file>.patch".
-      outname = (char*)malloc(strlen(target_filename) + 10);
-      strcpy(outname, target_filename);
-      strcat(outname, ".patch");
-
-      output = open(outname, O_WRONLY | O_CREAT | O_TRUNC);
-      if (output < 0) {
-        printf("failed to open output file %s: %s\n",
-               outname, strerror(errno));
-        return 1;
-      }
-      sink = FileSink;
-      token = &output;
-    }
-
-#define MAX_HEADER_LENGTH 8
-    unsigned char header[MAX_HEADER_LENGTH];
-    FILE* patchf = fopen(patch_filename, "rb");
-    if (patchf == NULL) {
-      printf("failed to open patch file %s: %s\n",
-             patch_filename, strerror(errno));
-      return 1;
-    }
-    int header_bytes_read = fread(header, 1, MAX_HEADER_LENGTH, patchf);
-    fclose(patchf);
-
-    SHA_init(&ctx);
-
-    int result;
-
-    if (header_bytes_read >= 4 &&
-        header[0] == 0xd6 && header[1] == 0xc3 &&
-        header[2] == 0xc4 && header[3] == 0) {
-      // xdelta3 patches begin "VCD" (with the high bits set) followed
-      // by a zero byte (the version number).
-      printf("error:  xdelta3 patches no longer supported\n");
-      return 1;
-    } else if (header_bytes_read >= 8 &&
-               memcmp(header, "BSDIFF40", 8) == 0) {
-      result = ApplyBSDiffPatch(source_to_use->data, source_to_use->size,
-                                    patch_filename, 0, sink, token, &ctx);
-    } else if (header_bytes_read >= 8 &&
-               memcmp(header, "IMGDIFF", 7) == 0 &&
-               (header[7] == '1' || header[7] == '2')) {
-      result = ApplyImagePatch(source_to_use->data, source_to_use->size,
-                                   patch_filename, sink, token, &ctx);
+    int retry = 1;
+    SHA_CTX ctx;
+    int output;
+    MemorySinkInfo msi;
+    FileContents* source_to_use;
+    char* outname;
+
+    // assume that target_filename (eg "/system/app/Foo.apk") is located
+    // on the same filesystem as its top-level directory ("/system").
+    // We need something that exists for calling statfs().
+    char target_fs[strlen(target_filename)+1];
+    char* slash = strchr(target_filename+1, '/');
+    if (slash != NULL) {
+        int count = slash - target_filename;
+        strncpy(target_fs, target_filename, count);
+        target_fs[count] = '\0';
     } else {
-      printf("Unknown patch file format\n");
-      return 1;
+        strcpy(target_fs, target_filename);
     }
 
-    if (output >= 0) {
-      fsync(output);
-      close(output);
+    do {
+        // Is there enough room in the target filesystem to hold the patched
+        // file?
+
+        if (strncmp(target_filename, "MTD:", 4) == 0) {
+            // If the target is an MTD partition, we're actually going to
+            // write the output to /tmp and then copy it to the partition.
+            // statfs() always returns 0 blocks free for /tmp, so instead
+            // we'll just assume that /tmp has enough space to hold the file.
+
+            // We still write the original source to cache, in case the MTD
+            // write is interrupted.
+            if (MakeFreeSpaceOnCache(source_file.size) < 0) {
+                printf("not enough free space on /cache\n");
+                return 1;
+            }
+            if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
+                printf("failed to back up source file\n");
+                return 1;
+            }
+            made_copy = 1;
+            retry = 0;
+        } else {
+            int enough_space = 0;
+            if (retry > 0) {
+                size_t free_space = FreeSpaceForFile(target_fs);
+                int enough_space =
+                    (free_space > (target_size * 3 / 2));  // 50% margin of error
+                printf("target %ld bytes; free space %ld bytes; retry %d; enough %d\n",
+                       (long)target_size, (long)free_space, retry, enough_space);
+            }
+
+            if (!enough_space) {
+                retry = 0;
+            }
+
+            if (!enough_space && source_patch_value != NULL) {
+                // Using the original source, but not enough free space.  First
+                // copy the source file to cache, then delete it from the original
+                // location.
+
+                if (strncmp(source_filename, "MTD:", 4) == 0) {
+                    // It's impossible to free space on the target filesystem by
+                    // deleting the source if the source is an MTD partition.  If
+                    // we're ever in a state where we need to do this, fail.
+                    printf("not enough free space for target but source is MTD\n");
+                    return 1;
+                }
+
+                if (MakeFreeSpaceOnCache(source_file.size) < 0) {
+                    printf("not enough free space on /cache\n");
+                    return 1;
+                }
+
+                if (SaveFileContents(CACHE_TEMP_SOURCE, source_file) < 0) {
+                    printf("failed to back up source file\n");
+                    return 1;
+                }
+                made_copy = 1;
+                unlink(source_filename);
+
+                size_t free_space = FreeSpaceForFile(target_fs);
+                printf("(now %ld bytes free for target)\n", (long)free_space);
+            }
+        }
+
+        const Value* patch;
+        if (source_patch_value != NULL) {
+            source_to_use = &source_file;
+            patch = source_patch_value;
+        } else {
+            source_to_use = &copy_file;
+            patch = copy_patch_value;
+        }
+
+        if (patch->type != VAL_BLOB) {
+            printf("patch is not a blob\n");
+            return 1;
+        }
+
+        SinkFn sink = NULL;
+        void* token = NULL;
+        output = -1;
+        outname = NULL;
+        if (strncmp(target_filename, "MTD:", 4) == 0) {
+            // We store the decoded output in memory.
+            msi.buffer = malloc(target_size);
+            if (msi.buffer == NULL) {
+                printf("failed to alloc %ld bytes for output\n",
+                       (long)target_size);
+                return 1;
+            }
+            msi.pos = 0;
+            msi.size = target_size;
+            sink = MemorySink;
+            token = &msi;
+        } else {
+            // We write the decoded output to "<tgt-file>.patch".
+            outname = (char*)malloc(strlen(target_filename) + 10);
+            strcpy(outname, target_filename);
+            strcat(outname, ".patch");
+
+            output = open(outname, O_WRONLY | O_CREAT | O_TRUNC);
+            if (output < 0) {
+                printf("failed to open output file %s: %s\n",
+                       outname, strerror(errno));
+                return 1;
+            }
+            sink = FileSink;
+            token = &output;
+        }
+
+        char* header = patch->data;
+        ssize_t header_bytes_read = patch->size;
+
+        SHA_init(&ctx);
+
+        int result;
+
+        if (header_bytes_read >= 8 &&
+            memcmp(header, "BSDIFF40", 8) == 0) {
+            result = ApplyBSDiffPatch(source_to_use->data, source_to_use->size,
+                                      patch, 0, sink, token, &ctx);
+        } else if (header_bytes_read >= 8 &&
+                   memcmp(header, "IMGDIFF2", 8) == 0) {
+            result = ApplyImagePatch(source_to_use->data, source_to_use->size,
+                                     patch, sink, token, &ctx);
+        } else {
+            printf("Unknown patch file format\n");
+            return 1;
+        }
+
+        if (output >= 0) {
+            fsync(output);
+            close(output);
+        }
+
+        if (result != 0) {
+            if (retry == 0) {
+                printf("applying patch failed\n");
+                return result != 0;
+            } else {
+                printf("applying patch failed; retrying\n");
+            }
+            if (outname != NULL) {
+                unlink(outname);
+            }
+        } else {
+            // succeeded; no need to retry
+            break;
+        }
+    } while (retry-- > 0);
+
+    const uint8_t* current_target_sha1 = SHA_final(&ctx);
+    if (memcmp(current_target_sha1, target_sha1, SHA_DIGEST_SIZE) != 0) {
+        printf("patch did not produce expected sha1\n");
+        return 1;
     }
 
-    if (result != 0) {
-      if (retry == 0) {
-        printf("applying patch failed\n");
-        return result != 0;
-      } else {
-        printf("applying patch failed; retrying\n");
-      }
-      if (outname != NULL) {
-        unlink(outname);
-      }
+    if (output < 0) {
+        // Copy the temp file to the MTD partition.
+        if (WriteToMTDPartition(msi.buffer, msi.pos, target_filename) != 0) {
+            printf("write of patched data to %s failed\n", target_filename);
+            return 1;
+        }
+        free(msi.buffer);
     } else {
-      // succeeded; no need to retry
-      break;
-    }
-  } while (retry-- > 0);
-
-  const uint8_t* current_target_sha1 = SHA_final(&ctx);
-  if (memcmp(current_target_sha1, target_sha1, SHA_DIGEST_SIZE) != 0) {
-    printf("patch did not produce expected sha1\n");
-    return 1;
-  }
-
-  if (output < 0) {
-    // Copy the temp file to the MTD partition.
-    if (WriteToMTDPartition(msi.buffer, msi.pos, target_filename) != 0) {
-      printf("write of patched data to %s failed\n", target_filename);
-      return 1;
-    }
-    free(msi.buffer);
-  } else {
-    // Give the .patch file the same owner, group, and mode of the
-    // original source file.
-    if (chmod(outname, source_to_use->st.st_mode) != 0) {
-      printf("chmod of \"%s\" failed: %s\n", outname, strerror(errno));
-      return 1;
-    }
-    if (chown(outname, source_to_use->st.st_uid,
-              source_to_use->st.st_gid) != 0) {
-      printf("chown of \"%s\" failed: %s\n", outname, strerror(errno));
-      return 1;
-    }
-
-    // Finally, rename the .patch file to replace the target file.
-    if (rename(outname, target_filename) != 0) {
-      printf("rename of .patch to \"%s\" failed: %s\n",
-              target_filename, strerror(errno));
-      return 1;
-    }
-  }
-
-  // If this run of applypatch created the copy, and we're here, we
-  // can delete it.
-  if (made_copy) unlink(CACHE_TEMP_SOURCE);
-
-  // Success!
-  return 0;
+        // Give the .patch file the same owner, group, and mode of the
+        // original source file.
+        if (chmod(outname, source_to_use->st.st_mode) != 0) {
+            printf("chmod of \"%s\" failed: %s\n", outname, strerror(errno));
+            return 1;
+        }
+        if (chown(outname, source_to_use->st.st_uid,
+                  source_to_use->st.st_gid) != 0) {
+            printf("chown of \"%s\" failed: %s\n", outname, strerror(errno));
+            return 1;
+        }
+
+        // Finally, rename the .patch file to replace the target file.
+        if (rename(outname, target_filename) != 0) {
+            printf("rename of .patch to \"%s\" failed: %s\n",
+                   target_filename, strerror(errno));
+            return 1;
+        }
+    }
+
+    // If this run of applypatch created the copy, and we're here, we
+    // can delete it.
+    if (made_copy) unlink(CACHE_TEMP_SOURCE);
+
+    // Success!
+    return 0;
 }