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Diffstat (limited to 'unwind_prot.c')
| -rw-r--r-- | unwind_prot.c | 326 |
1 files changed, 326 insertions, 0 deletions
diff --git a/unwind_prot.c b/unwind_prot.c new file mode 100644 index 0000000..9e150a6 --- /dev/null +++ b/unwind_prot.c @@ -0,0 +1,326 @@ +/* unwind_prot.c - a simple unwind-protect system for internal variables */ + +/* I can't stand it anymore! Please can't we just write the + whole Unix system in lisp or something? */ + +/* Copyright (C) 1987-2009 Free Software Foundation, Inc. + + This file is part of GNU Bash, the Bourne Again SHell. + + Bash is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + Bash is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with Bash. If not, see <http://www.gnu.org/licenses/>. +*/ + +/* **************************************************************** */ +/* */ +/* Unwind Protection Scheme for Bash */ +/* */ +/* **************************************************************** */ +#include "config.h" + +#include "bashtypes.h" +#include "bashansi.h" + +#if defined (HAVE_UNISTD_H) +# include <unistd.h> +#endif + +#if STDC_HEADERS +# include <stddef.h> +#endif + +#ifndef offsetof +# define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) +#endif + +#include "command.h" +#include "general.h" +#include "unwind_prot.h" +#include "quit.h" +#include "sig.h" + +/* Structure describing a saved variable and the value to restore it to. */ +typedef struct { + char *variable; + int size; + char desired_setting[1]; /* actual size is `size' */ +} SAVED_VAR; + +/* If HEAD.CLEANUP is null, then ARG.V contains a tag to throw back to. + If HEAD.CLEANUP is restore_variable, then SV.V contains the saved + variable. Otherwise, call HEAD.CLEANUP (ARG.V) to clean up. */ +typedef union uwp { + struct uwp_head { + union uwp *next; + Function *cleanup; + } head; + struct { + struct uwp_head uwp_head; + char *v; + } arg; + struct { + struct uwp_head uwp_head; + SAVED_VAR v; + } sv; +} UNWIND_ELT; + + +static void without_interrupts __P((VFunction *, char *, char *)); +static void unwind_frame_discard_internal __P((char *, char *)); +static void unwind_frame_run_internal __P((char *, char *)); +static void add_unwind_protect_internal __P((Function *, char *)); +static void remove_unwind_protect_internal __P((char *, char *)); +static void run_unwind_protects_internal __P((char *, char *)); +static void clear_unwind_protects_internal __P((char *, char *)); +static inline void restore_variable __P((SAVED_VAR *)); +static void unwind_protect_mem_internal __P((char *, char *)); + +static UNWIND_ELT *unwind_protect_list = (UNWIND_ELT *)NULL; + +#define uwpalloc(elt) (elt) = (UNWIND_ELT *)xmalloc (sizeof (UNWIND_ELT)) +#define uwpfree(elt) free(elt) + +/* Run a function without interrupts. This relies on the fact that the + FUNCTION cannot change the value of interrupt_immediately. (I.e., does + not call QUIT (). */ +static void +without_interrupts (function, arg1, arg2) + VFunction *function; + char *arg1, *arg2; +{ + int old_interrupt_immediately; + + old_interrupt_immediately = interrupt_immediately; + interrupt_immediately = 0; + + (*function)(arg1, arg2); + + interrupt_immediately = old_interrupt_immediately; +} + +/* Start the beginning of a region. */ +void +begin_unwind_frame (tag) + char *tag; +{ + add_unwind_protect ((Function *)NULL, tag); +} + +/* Discard the unwind protects back to TAG. */ +void +discard_unwind_frame (tag) + char *tag; +{ + if (unwind_protect_list) + without_interrupts (unwind_frame_discard_internal, tag, (char *)NULL); +} + +/* Run the unwind protects back to TAG. */ +void +run_unwind_frame (tag) + char *tag; +{ + if (unwind_protect_list) + without_interrupts (unwind_frame_run_internal, tag, (char *)NULL); +} + +/* Add the function CLEANUP with ARG to the list of unwindable things. */ +void +add_unwind_protect (cleanup, arg) + Function *cleanup; + char *arg; +{ + without_interrupts (add_unwind_protect_internal, (char *)cleanup, arg); +} + +/* Remove the top unwind protect from the list. */ +void +remove_unwind_protect () +{ + if (unwind_protect_list) + without_interrupts + (remove_unwind_protect_internal, (char *)NULL, (char *)NULL); +} + +/* Run the list of cleanup functions in unwind_protect_list. */ +void +run_unwind_protects () +{ + if (unwind_protect_list) + without_interrupts + (run_unwind_protects_internal, (char *)NULL, (char *)NULL); +} + +/* Erase the unwind-protect list. If flags is 1, free the elements. */ +void +clear_unwind_protect_list (flags) + int flags; +{ + char *flag; + + if (unwind_protect_list) + { + flag = flags ? "" : (char *)NULL; + without_interrupts + (clear_unwind_protects_internal, flag, (char *)NULL); + } +} + +int +have_unwind_protects () +{ + return (unwind_protect_list != 0); +} + +/* **************************************************************** */ +/* */ +/* The Actual Functions */ +/* */ +/* **************************************************************** */ + +static void +add_unwind_protect_internal (cleanup, arg) + Function *cleanup; + char *arg; +{ + UNWIND_ELT *elt; + + uwpalloc (elt); + elt->head.next = unwind_protect_list; + elt->head.cleanup = cleanup; + elt->arg.v = arg; + unwind_protect_list = elt; +} + +static void +remove_unwind_protect_internal (ignore1, ignore2) + char *ignore1, *ignore2; +{ + UNWIND_ELT *elt; + + elt = unwind_protect_list; + if (elt) + { + unwind_protect_list = unwind_protect_list->head.next; + uwpfree (elt); + } +} + +static void +run_unwind_protects_internal (ignore1, ignore2) + char *ignore1, *ignore2; +{ + unwind_frame_run_internal ((char *) NULL, (char *) NULL); +} + +static void +clear_unwind_protects_internal (flag, ignore) + char *flag, *ignore; +{ + if (flag) + { + while (unwind_protect_list) + remove_unwind_protect_internal ((char *)NULL, (char *)NULL); + } + unwind_protect_list = (UNWIND_ELT *)NULL; +} + +static void +unwind_frame_discard_internal (tag, ignore) + char *tag, *ignore; +{ + UNWIND_ELT *elt; + + while (elt = unwind_protect_list) + { + unwind_protect_list = unwind_protect_list->head.next; + if (elt->head.cleanup == 0 && (STREQ (elt->arg.v, tag))) + { + uwpfree (elt); + break; + } + else + uwpfree (elt); + } +} + +/* Restore the value of a variable, based on the contents of SV. + sv->desired_setting is a block of memory SIZE bytes long holding the + value itself. This block of memory is copied back into the variable. */ +static inline void +restore_variable (sv) + SAVED_VAR *sv; +{ + FASTCOPY (sv->desired_setting, sv->variable, sv->size); +} + +static void +unwind_frame_run_internal (tag, ignore) + char *tag, *ignore; +{ + UNWIND_ELT *elt; + + while (elt = unwind_protect_list) + { + unwind_protect_list = elt->head.next; + + /* If tag, then compare. */ + if (!elt->head.cleanup) + { + if (tag && STREQ (elt->arg.v, tag)) + { + uwpfree (elt); + break; + } + } + else + { + if (elt->head.cleanup == (Function *) restore_variable) + restore_variable (&elt->sv.v); + else + (*(elt->head.cleanup)) (elt->arg.v); + } + + uwpfree (elt); + } +} + +static void +unwind_protect_mem_internal (var, psize) + char *var; + char *psize; +{ + int size, allocated; + UNWIND_ELT *elt; + + size = *(int *) psize; + allocated = size + offsetof (UNWIND_ELT, sv.v.desired_setting[0]); + elt = (UNWIND_ELT *)xmalloc (allocated); + elt->head.next = unwind_protect_list; + elt->head.cleanup = (Function *) restore_variable; + elt->sv.v.variable = var; + elt->sv.v.size = size; + FASTCOPY (var, elt->sv.v.desired_setting, size); + unwind_protect_list = elt; +} + +/* Save the value of a variable so it will be restored when unwind-protects + are run. VAR is a pointer to the variable. SIZE is the size in + bytes of VAR. */ +void +unwind_protect_mem (var, size) + char *var; + int size; +{ + without_interrupts (unwind_protect_mem_internal, var, (char *) &size); +} |