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