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Diffstat (limited to 'WebCore/platform/graphics/chromium/VDMXParser.cpp')
| -rw-r--r-- | WebCore/platform/graphics/chromium/VDMXParser.cpp | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/WebCore/platform/graphics/chromium/VDMXParser.cpp b/WebCore/platform/graphics/chromium/VDMXParser.cpp new file mode 100644 index 0000000..3347226 --- /dev/null +++ b/WebCore/platform/graphics/chromium/VDMXParser.cpp @@ -0,0 +1,203 @@ +/* + * Copyright (c) 2008, 2009, Google Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following disclaimer + * in the documentation and/or other materials provided with the + * distribution. + * * Neither the name of Google Inc. nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <sys/types.h> + +// For htons/ntohs +#include <arpa/inet.h> + +// Buffer helper class +// +// This class perform some trival buffer operations while checking for +// out-of-bounds errors. As a family they return false if anything is amiss, +// updating the current offset otherwise. +class Buffer { +public: + Buffer(const uint8_t* buffer, size_t length) + : m_buffer(buffer) + , m_length(length) + , m_offset(0) { } + + bool skip(size_t numBytes) + { + if (m_offset + numBytes > m_length) + return false; + m_offset += numBytes; + return true; + } + + bool readU8(uint8_t* value) + { + if (m_offset + sizeof(uint8_t) > m_length) + return false; + *value = m_buffer[m_offset]; + m_offset += sizeof(uint8_t); + return true; + } + + bool readU16(uint16_t* value) + { + if (m_offset + sizeof(uint16_t) > m_length) + return false; + memcpy(value, m_buffer + m_offset, sizeof(uint16_t)); + *value = ntohs(*value); + m_offset += sizeof(uint16_t); + return true; + } + + bool readS16(int16_t* value) + { + return readU16(reinterpret_cast<uint16_t*>(value)); + } + + size_t offset() const + { + return m_offset; + } + + void setOffset(size_t newoffset) + { + m_offset = newoffset; + } + +private: + const uint8_t *const m_buffer; + const size_t m_length; + size_t m_offset; +}; + +// VDMX parsing code. +// +// VDMX tables are found in some TrueType/OpenType fonts and contain +// ascender/descender overrides for certain (usually small) sizes. This is +// needed in order to match font metrics on Windows. +// +// Freetype does not parse these tables so we do so here. + +namespace WebCore { + +// Parse a TrueType VDMX table. +// yMax: (output) the ascender value from the table +// yMin: (output) the descender value from the table (negative!) +// vdmx: the table bytes +// vdmxLength: length of @vdmx, in bytes +// targetPixelSize: the pixel size of the font (e.g. 16) +// +// Returns true iff a suitable match are found. Otherwise, *yMax and *yMin are +// untouched. size_t must be 32-bits to avoid overflow. +// +// See http://www.microsoft.com/opentype/otspec/vdmx.htm +bool parseVDMX(int* yMax, int* yMin, + const uint8_t* vdmx, size_t vdmxLength, + unsigned targetPixelSize) +{ + Buffer buf(vdmx, vdmxLength); + + // We ignore the version. Future tables should be backwards compatible with + // this layout. + uint16_t numRatios; + if (!buf.skip(4) || !buf.readU16(&numRatios)) + return false; + + // Now we have two tables. Firstly we have @numRatios Ratio records, then a + // matching array of @numRatios offsets. We save the offset of the beginning + // of this second table. + // + // Range 6 <= x <= 262146 + unsigned long offsetTableOffset = + buf.offset() + 4 /* sizeof struct ratio */ * numRatios; + + unsigned desiredRatio = 0xffffffff; + // We read 4 bytes per record, so the offset range is + // 6 <= x <= 524286 + for (unsigned i = 0; i < numRatios; ++i) { + uint8_t xRatio, yRatio1, yRatio2; + + if (!buf.skip(1) + || !buf.readU8(&xRatio) + || !buf.readU8(&yRatio1) + || !buf.readU8(&yRatio2)) + return false; + + // This either covers 1:1, or this is the default entry (0, 0, 0) + if ((xRatio == 1 && yRatio1 <= 1 && yRatio2 >= 1) + || (xRatio == 0 && yRatio1 == 0 && yRatio2 == 0)) { + desiredRatio = i; + break; + } + } + + if (desiredRatio == 0xffffffff) // no ratio found + return false; + + // Range 10 <= x <= 393216 + buf.setOffset(offsetTableOffset + sizeof(uint16_t) * desiredRatio); + + // Now we read from the offset table to get the offset of another array + uint16_t groupOffset; + if (!buf.readU16(&groupOffset)) + return false; + // Range 0 <= x <= 65535 + buf.setOffset(groupOffset); + + uint16_t numRecords; + if (!buf.readU16(&numRecords) || !buf.skip(sizeof(uint16_t))) + return false; + + // We read 6 bytes per record, so the offset range is + // 4 <= x <= 458749 + for (unsigned i = 0; i < numRecords; ++i) { + uint16_t pixelSize; + if (!buf.readU16(&pixelSize)) + return false; + // the entries are sorted, so we can abort early if need be + if (pixelSize > targetPixelSize) + return false; + + if (pixelSize == targetPixelSize) { + int16_t tempYMax, tempYMin; + if (!buf.readS16(&tempYMax) + || !buf.readS16(&tempYMin)) + return false; + *yMin = tempYMin; + *yMax = tempYMax; + return true; + } + if (!buf.skip(2 * sizeof(int16_t))) + return false; + } + + return false; +} + +} // namespace WebCore |