Remove content/browser dependency on WebFontRenderStyle.

content/common/common_sandbox_support_linux.cc

+// 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 "content/public/common/common_sandbox_support_linux.h"
+
+#include <stddef.h>
+#include <sys/stat.h>
+
+#include <limits>
+#include <memory>
+
+#include "base/numerics/safe_conversions.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/sys_byteorder.h"
+#include "base/trace_event/trace_event.h"
+
+namespace content {
+
+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 content