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http://www.2net.co.uk/tutorial/android-sparse-image-format
system/core/libsparse/backed_block.h
enum backed_block_type {
BACKED_BLOCK_DATA,
BACKED_BLOCK_FILE,
BACKED_BLOCK_FD,
BACKED_BLOCK_FILL,
};
struct backed_block {
unsigned int block;
unsigned int len;
enum backed_block_type type;
union {
struct {
void *data;
} data;
struct {
char *filename;
int64_t offset;
} file;
struct {
int fd;
int64_t offset;
} fd;
struct {
uint32_t val;
} fill;
};
struct backed_block *next;
};
system/core/libsparse/sparse_format.h
typedef struct sparse_header {
__le32 magic; /* 0xed26ff3a */
__le16 major_version; /* (0x1) - reject images with higher major versions */
__le16 minor_version; /* (0x0) - allow images with higer minor versions */
__le16 file_hdr_sz; /* 28 bytes for first revision of the file format */
__le16 chunk_hdr_sz; /* 12 bytes for first revision of the file format */
__le32 blk_sz; /* block size in bytes, must be a multiple of 4 (4096) */
__le32 total_blks; /* total blocks in the non-sparse output image */
__le32 total_chunks; /* total chunks in the sparse input image */
__le32 image_checksum; /* CRC32 checksum of the original data, counting "don't care" */
/* as 0. Standard 802.3 polynomial, use a Public Domain */
/* table implementation */
} sparse_header_t;
#define SPARSE_HEADER_MAGIC 0xed26ff3a
#define CHUNK_TYPE_RAW 0xCAC1
#define CHUNK_TYPE_FILL 0xCAC2
#define CHUNK_TYPE_DONT_CARE 0xCAC3
#define CHUNK_TYPE_CRC32 0xCAC4
typedef struct chunk_header {
__le16 chunk_type; /* 0xCAC1 -> raw; 0xCAC2 -> fill; 0xCAC3 -> don't care */
__le16 reserved1;
__le32 chunk_sz; /* in blocks in output image */
__le32 total_sz; /* in bytes of chunk input file including chunk header and data */
} chunk_header_t;
/* Following a Raw or Fill or CRC32 chunk is data.
* For a Raw chunk, it's the data in chunk_sz * blk_sz.
* For a Fill chunk, it's 4 bytes of the fill data.
* For a CRC32 chunk, it's 4 bytes of CRC32
*/
sparse_header_t sparse_header = {
.magic = SPARSE_HEADER_MAGIC,
.major_version = SPARSE_HEADER_MAJOR_VER,
.minor_version = SPARSE_HEADER_MINOR_VER,
.file_hdr_sz = SPARSE_HEADER_LEN,
.chunk_hdr_sz = CHUNK_HEADER_LEN,
.blk_sz = out->block_size,
.total_blks = out->len / out->block_size,
.total_chunks = chunks,
.image_checksum = 0
};
binary:
./out/host/linux-x86/bin/fastboot
./out/host/linux-x86/bin/simg2img
./out/host/linux-x86/bin/img2simg
./system/core/libsparse/simg_dump.py
files:
system/core/libsparse/output_file.c
./system/core/libsparse/simg_dump.py
system/core/libsparse/sparse.c
system/core/libsparse/backed_block.c
bb->type = BACKED_BLOCK_FILL <- backed_block_add_fill <- sparse_file_add_fill
system/core/libsparse/sparse_read.c
sparse_file_read->sparse_file_read_normal->sparse_file_add_fill
process_chunk->process_fill_chunk->sparse_file_add_fill
sparse_file_import_auto:
sparse_file_import
sparse_file_new
sparse_file_read_normal
system/core/libsparse/img2simg.c
main:
sparse_file_new
sparse_file_verbose
sparse_file_read in system/core/libsparse/sparse_read.c
sparse_file_write
sparse_count_chunks
output_file_open_fd
write_all_blocks
sparse_file_write_block
BACKED_BLOCK_DATA: write_data_chunk
BACKED_BLOCK_FILE: write_file_chunk
BACKED_BLOCK_FD: write_fd_chunk
BACKED_BLOCK_FILL: write_fill_chunk
system/core/libsparse/simg2img.c
main:
sparse_file_import
sparse_file_write
system/core/fastboot/fastboot.cpp:
main:
branch "flash" -- do_flash:
load_buf:
load_buf_fd:
get_sparse_limit
load_sparse_files
sparse_file_import_auto
sparse_file_import
sparse_file_new
sparse_file_read_normal
sparse_file_resparse
sparse_file_resparse
sparse_file_new
move_chunks_up_to_len
backed_block_list_move
buf->type = FB_BUFFER_SPARSE
buf->data = s
flash_buf:
sparse_file_len
fb_queue_flash_sparse
device/linaro/bootloader/OpenPlatformPkg/Platforms/Hisilicon/HiKey/HiKeyFastbootDxe/HiKeyFastboot.c
HiKeyFastbootPlatformFlashPartition
============== CHUNK_TYPE_DONT_CARE ================
system/core/libsparse/output_file.c
write_sparse_skip_chunk
<-- write_all_blocks in libsparse/sparse.c
system/core/libsparse/sparse_read.c
process_chunk
CHUNK_TYPE_FILL: process_fill_chunk
CHUNK_TYPE_DONT_CARE: process_skip_chunk
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