1 /////////////////////////////////////////////////////////////////////////////// 2 // 3 /// \file vli_encoder.c 4 /// \brief Encodes variable-length integers 5 // 6 // Author: Lasse Collin 7 // 8 // This file has been put into the public domain. 9 // You can do whatever you want with this file. 10 // 11 /////////////////////////////////////////////////////////////////////////////// 12 13 #include "common.h" 14 15 16 extern LZMA_API(lzma_ret) 17 lzma_vli_encode(lzma_vli vli, size_t *vli_pos, 18 uint8_t *restrict out, size_t *restrict out_pos, 19 size_t out_size) 20 { 21 // If we haven't been given vli_pos, work in single-call mode. 22 size_t vli_pos_internal = 0; 23 if (vli_pos == NULL) { 24 vli_pos = &vli_pos_internal; 25 26 // In single-call mode, we expect that the caller has 27 // reserved enough output space. 28 if (*out_pos >= out_size) 29 return LZMA_PROG_ERROR; 30 } else { 31 // This never happens when we are called by liblzma, but 32 // may happen if called directly from an application. 33 if (*out_pos >= out_size) 34 return LZMA_BUF_ERROR; 35 } 36 37 // Validate the arguments. 38 if (*vli_pos >= LZMA_VLI_BYTES_MAX || vli > LZMA_VLI_MAX) 39 return LZMA_PROG_ERROR; 40 41 // Shift vli so that the next bits to encode are the lowest. In 42 // single-call mode this never changes vli since *vli_pos is zero. 43 vli >>= *vli_pos * 7; 44 45 // Write the non-last bytes in a loop. 46 while (vli >= 0x80) { 47 // We don't need *vli_pos during this function call anymore, 48 // but update it here so that it is ready if we need to 49 // return before the whole integer has been decoded. 50 ++*vli_pos; 51 assert(*vli_pos < LZMA_VLI_BYTES_MAX); 52 53 // Write the next byte. 54 out[*out_pos] = (uint8_t)(vli) | 0x80; 55 vli >>= 7; 56 57 if (++*out_pos == out_size) 58 return vli_pos == &vli_pos_internal 59 ? LZMA_PROG_ERROR : LZMA_OK; 60 } 61 62 // Write the last byte. 63 out[*out_pos] = (uint8_t)(vli); 64 ++*out_pos; 65 ++*vli_pos; 66 67 return vli_pos == &vli_pos_internal ? LZMA_OK : LZMA_STREAM_END; 68 69 } 70