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- // Copyright 2017 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "pdf/font_table_linux.h"
- #include <sys/stat.h>
- #include <unistd.h>
- #include <algorithm>
- #include <limits>
- #include <memory>
- #include "base/numerics/safe_conversions.h"
- #include "base/posix/eintr_wrapper.h"
- #include "base/sys_byteorder.h"
- namespace pdf {
- // TODO(drott): This should be should be replaced with using FreeType for the
- // purpose instead of reimplementing table parsing.
- bool GetFontTable(int fd,
- uint32_t table_tag,
- off_t offset,
- uint8_t* output,
- size_t* output_length) {
- if (offset < 0)
- return false;
- size_t data_length = 0; // the length of the file data.
- off_t data_offset = 0; // the offset of the data in the file.
- if (table_tag == 0) {
- // Get the entire font file.
- struct stat st;
- if (fstat(fd, &st) < 0)
- return false;
- data_length = base::checked_cast<size_t>(st.st_size);
- } else {
- // Get a font table. Read the header to find its offset in the file.
- uint16_t num_tables;
- ssize_t n = HANDLE_EINTR(
- pread(fd, &num_tables, sizeof(num_tables), 4 /* skip the font type */));
- if (n != sizeof(num_tables))
- return false;
- // Font data is stored in net (big-endian) order.
- num_tables = base::NetToHost16(num_tables);
- // Read the table directory.
- static const size_t kTableEntrySize = 16;
- const size_t directory_size = num_tables * kTableEntrySize;
- std::unique_ptr<uint8_t[]> table_entries(new uint8_t[directory_size]);
- n = HANDLE_EINTR(pread(fd, table_entries.get(), directory_size,
- 12 /* skip the SFNT header */));
- if (n != base::checked_cast<ssize_t>(directory_size))
- return false;
- for (uint16_t i = 0; i < num_tables; ++i) {
- uint8_t* entry = table_entries.get() + i * kTableEntrySize;
- uint32_t tag = *reinterpret_cast<uint32_t*>(entry);
- if (tag == table_tag) {
- // Font data is stored in net (big-endian) order.
- data_offset =
- base::NetToHost32(*reinterpret_cast<uint32_t*>(entry + 8));
- data_length =
- base::NetToHost32(*reinterpret_cast<uint32_t*>(entry + 12));
- break;
- }
- }
- }
- if (!data_length)
- return false;
- // Clamp |offset| inside the allowable range. This allows the read to succeed
- // but return 0 bytes.
- offset = std::min(offset, base::checked_cast<off_t>(data_length));
- // Make sure it's safe to add the data offset and the caller's logical offset.
- // Define the maximum positive offset on 32 bit systems.
- static const off_t kMaxPositiveOffset32 = 0x7FFFFFFF; // 2 GB - 1.
- if ((offset > kMaxPositiveOffset32 / 2) ||
- (data_offset > kMaxPositiveOffset32 / 2))
- return false;
- data_offset += offset;
- data_length -= offset;
- if (output) {
- // 'output_length' holds the maximum amount of data the caller can accept.
- data_length = std::min(data_length, *output_length);
- ssize_t n = HANDLE_EINTR(pread(fd, output, data_length, data_offset));
- if (n != base::checked_cast<ssize_t>(data_length))
- return false;
- }
- *output_length = data_length;
- return true;
- }
- } // namespace pdf
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