Add a variable-length header region to the binary format.
Also bump up the format version to 2.
Bug: 5686638
Change-Id: I3aafdd7e42c422202122998ec093280051aa8e07
diff --git a/native/src/binary_format.h b/native/src/binary_format.h
index 1d74998..ab033ad 100644
--- a/native/src/binary_format.h
+++ b/native/src/binary_format.h
@@ -17,6 +17,7 @@
#ifndef LATINIME_BINARY_FORMAT_H
#define LATINIME_BINARY_FORMAT_H
+#include <limits>
#include "unigram_dictionary.h"
namespace latinime {
@@ -29,10 +30,18 @@
public:
const static int UNKNOWN_FORMAT = -1;
- const static int FORMAT_VERSION_1 = 1;
- const static uint16_t FORMAT_VERSION_1_MAGIC_NUMBER = 0x78B1;
+ // Originally, format version 1 had a 16-bit magic number, then the version number `01'
+ // then options that must be 0. Hence the first 32-bits of the format are always as follow
+ // and it's okay to consider them a magic number as a whole.
+ const static uint32_t FORMAT_VERSION_1_MAGIC_NUMBER = 0x78B10100;
+ const static unsigned int FORMAT_VERSION_1_HEADER_SIZE = 5;
+ // The versions of Latin IME that only handle format version 1 only test for the magic
+ // number, so we had to change it so that version 2 files would be rejected by older
+ // implementations. On this occasion, we made the magic number 32 bits long.
+ const static uint32_t FORMAT_VERSION_2_MAGIC_NUMBER = 0x9BC13AFE;
static int detectFormat(const uint8_t* const dict);
+ static unsigned int getHeaderSize(const uint8_t* const dict);
static int getGroupCountAndForwardPointer(const uint8_t* const dict, int* pos);
static uint8_t getFlagsAndForwardPointer(const uint8_t* const dict, int* pos);
static int32_t getCharCodeAndForwardPointer(const uint8_t* const dict, int* pos);
@@ -55,9 +64,37 @@
};
inline int BinaryFormat::detectFormat(const uint8_t* const dict) {
- const uint16_t magicNumber = (dict[0] << 8) + dict[1]; // big endian
- if (FORMAT_VERSION_1_MAGIC_NUMBER == magicNumber) return FORMAT_VERSION_1;
- return UNKNOWN_FORMAT;
+ // The magic number is stored big-endian.
+ const uint32_t magicNumber = (dict[0] << 24) + (dict[1] << 16) + (dict[2] << 8) + dict[3];
+ switch (magicNumber) {
+ case FORMAT_VERSION_1_MAGIC_NUMBER:
+ // Format 1 header is exactly 5 bytes long and looks like:
+ // Magic number (2 bytes) 0x78 0xB1
+ // Version number (1 byte) 0x01
+ // Options (2 bytes) must be 0x00 0x00
+ return 1;
+ case FORMAT_VERSION_2_MAGIC_NUMBER:
+ // Format 2 header is as follows:
+ // Magic number (4 bytes) 0x9B 0xC1 0x3A 0xFE
+ // Version number (2 bytes) 0x00 0x02
+ // Options (2 bytes) must be 0x00 0x00
+ // Header size (4 bytes) : integer, big endian
+ return (dict[4] << 8) + dict[5];
+ default:
+ return UNKNOWN_FORMAT;
+ }
+}
+
+inline unsigned int BinaryFormat::getHeaderSize(const uint8_t* const dict) {
+ switch (detectFormat(dict)) {
+ case 1:
+ return FORMAT_VERSION_1_HEADER_SIZE;
+ case 2:
+ // See the format of the header in the comment in detectFormat() above
+ return (dict[8] << 24) + (dict[9] << 16) + (dict[10] << 8) + dict[11];
+ default:
+ return std::numeric_limits<unsigned int>::max();
+ }
}
inline int BinaryFormat::getGroupCountAndForwardPointer(const uint8_t* const dict, int* pos) {