Simple PMP reader to parse Picasa's metadata

webkit/fileapi/media/picasa/pmp_column_reader.cc

+// Copyright 2013 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 "webkit/fileapi/media/picasa/pmp_column_reader.h"
+
+#include <cstring>
+
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/threading/thread_restrictions.h"
+#include "webkit/fileapi/media/picasa/pmp_constants.h"
+
+namespace picasaimport {
+
+namespace {
+
+const size_t kPmpMaxFilesize = 50*1024*1024; // Maximum of 50 MB.
+
+}  // namespace
+
+PmpColumnReader::PmpColumnReader()
+    : data_(NULL),
+      length_(0),
+      field_type_(INVALID_TYPE),
+      rows_(0),
+      strings_() { }
+
+PmpColumnReader::~PmpColumnReader() { }
+
+bool PmpColumnReader::Init(const base::FilePath& filepath, uint32* rows_read) {
+  DCHECK(!data_.get());
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  long int length = 0; // Signed temporary.
+  if (!file_util::GetFileSize(filepath, &length))
+    return false;
+
+  length_ = length;
+
+  if (length_ < kPmpHeaderSize || length_ > kPmpMaxFilesize)
+    return false;
+
+  data_.reset(new uint8[length_]);
+
+  char* data_begin = reinterpret_cast<char*>(data_.get());
+
+  return file_util::ReadFile(filepath, data_begin, length_) &&
+         ParseData(rows_read);
+}
+
+bool PmpColumnReader::ReadString(const uint32 row, std::string* result) const {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GT(length_, kPmpHeaderSize + row);
+
+  if (field_type_ != STRING_TYPE || row >= rows_)
+    return false;
+
+  *result = strings_[row];
+  return true;
+}
+
+bool PmpColumnReader::ReadUInt32(const uint32 row, uint32* result) const {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GT(length_, kPmpHeaderSize + row * sizeof(uint32));
+
+  if (field_type_ != UINT32_TYPE || row >= rows_)
+    return false;
+
+  *result = reinterpret_cast<uint32*>(data_.get() + kPmpHeaderSize)[row];
+  return true;
+}
+
+bool PmpColumnReader::ReadDouble64(const uint32 row, double* result) const {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GT(length_, kPmpHeaderSize + row * sizeof(double));
+
+  if (field_type_ != DOUBLE64_TYPE || row >= rows_)
+    return false;
+
+  *result = reinterpret_cast<double*>(data_.get() + kPmpHeaderSize)[row];
+  return true;
+}
+
+bool PmpColumnReader::ReadUInt8(const uint32 row, uint8* result) const {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GT(length_, kPmpHeaderSize + row * sizeof(uint8));
+
+  if (field_type_ != UINT8_TYPE || row >= rows_)
+    return false;
+
+  *result = reinterpret_cast<uint8*>(data_.get() + kPmpHeaderSize)[row];
+  return true;
+}
+
+bool PmpColumnReader::ReadUInt64(const uint32 row, uint64* result) const {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GT(length_, kPmpHeaderSize + row * sizeof(uint64));
+
+  if (field_type_ != UINT64_TYPE || row >= rows_)
+    return false;
+
+  *result = reinterpret_cast<uint64*>(data_.get() + kPmpHeaderSize)[row];
+  return true;
+}
+
+bool PmpColumnReader::ParseData(uint32* rows_read) {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GE(length_, kPmpHeaderSize);
+
+  // Check all magic bytes.
+  if (memcmp(&kPmpMagic1, &data_[kPmpMagic1Offset], sizeof(kPmpMagic1)) != 0 ||
+      memcmp(&kPmpMagic2, &data_[kPmpMagic2Offset], sizeof(kPmpMagic2)) != 0 ||
+      memcmp(&kPmpMagic3, &data_[kPmpMagic3Offset], sizeof(kPmpMagic3)) != 0 ||
+      memcmp(&kPmpMagic4, &data_[kPmpMagic4Offset], sizeof(kPmpMagic4)) != 0) {
+    return false;
+  }
+
+  field_type_ = *(reinterpret_cast<uint16*>(&data_[kPmpFieldType1Offset]));
+
+  // Verify if field type matches second declaration
+  if (field_type_ != *(reinterpret_cast<uint16*>(&data_[kPmpFieldType2Offset])))
+    return false;
+
+  rows_ = *(reinterpret_cast<uint32*>(&data_[kPmpRowCountOffset]));
+
+  size_t body_length = length_ - kPmpHeaderSize;
+  size_t expected_body_length = 0;
+  switch (field_type_) {
+    case STRING_TYPE:
+      expected_body_length = IndexStrings();
+      break;
+    case UINT32_TYPE:
+      expected_body_length = rows_ * sizeof(uint32);
+      break;
+    case DOUBLE64_TYPE:
+      expected_body_length = rows_ * sizeof(double);
+      break;
+    case UINT8_TYPE:
+      expected_body_length = rows_ * sizeof(uint8);
+      break;
+    case UINT64_TYPE:
+      expected_body_length = rows_ * sizeof(uint64);
+      break;
+    default:
+      return false;
+      break;
+  }
+
+  if (body_length == expected_body_length && rows_read)
+    *rows_read = rows_;
+  return body_length == expected_body_length;
+}
+
+long PmpColumnReader::IndexStrings() {
+  DCHECK(data_.get() != NULL);
+  DCHECK_GE(length_, kPmpHeaderSize);
+
+  strings_.reserve(rows_);
+
+  size_t bytes_parsed = kPmpHeaderSize;
+  const uint8* data_cursor = data_.get() + kPmpHeaderSize;
+
+  while (strings_.size() < rows_) {
+    const uint8* string_end = static_cast<const uint8*>(
+        memchr(data_cursor, '\0', length_ - bytes_parsed));
+
+    // Fail if cannot find null termination. String runs on past file end.
+    if (string_end == NULL)
+      return -1;
+
+    // Length of string. (+1 to include the termination character).
+    ptrdiff_t length_in_bytes = string_end - data_cursor + 1;
+
+    strings_.push_back(reinterpret_cast<const char*>(data_cursor));
+    data_cursor += length_in_bytes;
+    bytes_parsed += length_in_bytes;
+  }
+
+  return bytes_parsed - kPmpHeaderSize;
+}
+
+}  // namespace picasaimport