98 lines
3.4 KiB
C++
98 lines
3.4 KiB
C++
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#define _GNU_SOURCE
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/sendfile.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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typedef struct sparse_header {
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uint32_t magic; /* 0xed26ff3a */
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uint16_t major_version; /* (0x1) - reject images with higher major versions */
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uint16_t minor_version; /* (0x0) - allow images with higer minor versions */
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uint16_t file_hdr_sz; /* 28 bytes for first revision of the file format */
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uint16_t chunk_hdr_sz; /* 12 bytes for first revision of the file format */
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uint32_t blk_sz; /* block size in bytes, must be a multiple of 4 (4096) */
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uint32_t total_blks; /* total blocks in the non-sparse output image */
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uint32_t total_chunks; /* total chunks in the sparse input image */
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uint32_t image_checksum; /* CRC32 checksum of the original data, counting "don't care" */
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/* as 0. Standard 802.3 polynomial, use a Public Domain */
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/* table implementation */
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} sparse_header_t;
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#define SPARSE_HEADER_MAGIC 0xed26ff3a
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#define CHUNK_TYPE_RAW 0xCAC1
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#define CHUNK_TYPE_FILL 0xCAC2
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#define CHUNK_TYPE_DONT_CARE 0xCAC3
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#define CHUNK_TYPE_CRC32 0xCAC4
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typedef struct chunk_header {
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uint16_t chunk_type; /* 0xCAC1 -> raw; 0xCAC2 -> fill; 0xCAC3 -> don't care */
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uint16_t reserved1;
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uint32_t chunk_sz; /* in blocks in output image */
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uint32_t total_sz; /* in bytes of chunk input file including chunk header and data */
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} chunk_header_t;
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/* Following a Raw or Fill or CRC32 chunk is data.
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* For a Raw chunk, it's the data in chunk_sz * blk_sz.
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* For a Fill chunk, it's 4 bytes of the fill data.
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* For a CRC32 chunk, it's 4 bytes of CRC32
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*/
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void nsendfile(int out_fd, int in_fd, size_t count) {
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while(count) {
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ssize_t res = splice(in_fd, NULL, out_fd, NULL, count, 0);
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if(res == 0 || res == -1) exit(112);
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count -= res;
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}
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}
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int main() {
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sparse_header_t hdr;
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if(read(0, &hdr, sizeof(hdr)) != sizeof(hdr)) exit(1);
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if(hdr.magic != SPARSE_HEADER_MAGIC) exit(2);
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if(hdr.blk_sz != 4096) exit(6);
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if(hdr.major_version != 1) exit(11);
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if(hdr.minor_version != 0) exit(12);
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if(hdr.file_hdr_sz != 28) exit(13);
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if(hdr.chunk_hdr_sz != 12) exit(14);
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char block[4096];
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for(unsigned i=0; i<hdr.total_chunks; i++) {
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chunk_header_t chunk;
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if(read(0, &chunk, sizeof(chunk)) != sizeof(chunk)) exit(3);
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if(chunk.chunk_type == CHUNK_TYPE_RAW) {
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if(chunk.total_sz != sizeof(chunk_header_t) + (chunk.chunk_sz * hdr.blk_sz)) exit(7);
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nsendfile(1, 0, hdr.blk_sz * chunk.chunk_sz);
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} else if(chunk.chunk_type == CHUNK_TYPE_FILL) {
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if(chunk.total_sz != 4 + sizeof(chunk_header_t)) exit(7);
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uint32_t fill;
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if(read(0, &fill, sizeof(fill)) != sizeof(fill)) exit(5);
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//memset takes a char, not a int32, hence the check
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if(fill != 0) exit(6);
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memset(block, fill, hdr.blk_sz);
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for(unsigned i=0; i<chunk.chunk_sz; i++)
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if(write(1, block, hdr.blk_sz) != hdr.blk_sz) exit(8);
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} else if(chunk.chunk_type == CHUNK_TYPE_DONT_CARE) {
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if(chunk.total_sz != sizeof(chunk_header_t)) exit(9);
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memset(block, 0, hdr.blk_sz);
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for(unsigned i=0; i<chunk.chunk_sz; i++)
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if(write(1, block, hdr.blk_sz) != hdr.blk_sz) exit(10);
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} else if(chunk.chunk_type == CHUNK_TYPE_CRC32) {
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if(chunk.total_sz != 4 + sizeof(chunk_header_t)) exit(7);
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uint32_t crc32;
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if(read(0, &crc32, sizeof(crc32)) != sizeof(crc32)) exit(5);
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/* ignore crc32 */
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} else {
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exit(4);
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}
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}
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fsync(1);
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return 0;
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}
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