diff options
Diffstat (limited to 'src/lzw.c')
| -rw-r--r-- | src/lzw.c | 27 |
1 files changed, 13 insertions, 14 deletions
@@ -301,7 +301,7 @@ lzw_result lzw_decode(struct lzw_ctx *ctx, lzw_result res; uint32_t code_new; uint32_t code_out; - struct lzw_dictionary_entry *entry; + uint8_t last_value; uint8_t *stack_pos = ctx->stack_base; uint32_t clear_code = ctx->clear_code; uint32_t current_entry = ctx->current_entry; @@ -322,28 +322,28 @@ lzw_result lzw_decode(struct lzw_ctx *ctx, return LZW_EOI_CODE; } - if (current_entry >= (1 << LZW_CODE_MAX)) { - /* No space in table for new entries, only Clear and - * End of Information codes were allowed. */ - return LZW_BAD_DATA; - } - - entry = table + current_entry; if (code_new > current_entry) { /* Code is invalid */ return LZW_BAD_CODE; } else if (code_new < current_entry) { /* Code is in table */ code_out = code_new; - entry->last_value = table[code_new].first_value; + last_value = table[code_new].first_value; } else { /* Code not in table */ *stack_pos++ = ctx->previous_code_first; code_out = ctx->previous_code; - entry->last_value = ctx->previous_code_first; + last_value = ctx->previous_code_first; + } + + /* Add to the dictionary, only if there's space */ + if (current_entry < (1 << LZW_CODE_MAX)) { + struct lzw_dictionary_entry *entry = table + current_entry; + entry->last_value = last_value; + entry->first_value = ctx->previous_code_first; + entry->previous_entry = ctx->previous_code; + ctx->current_entry++; } - entry->first_value = ctx->previous_code_first; - entry->previous_entry = ctx->previous_code; /* Ensure code size is increased, if needed. */ if (current_entry == ctx->current_code_size_max) { @@ -353,7 +353,6 @@ lzw_result lzw_decode(struct lzw_ctx *ctx, (1 << ctx->current_code_size) - 1; } } - ctx->current_entry++; ctx->previous_code_first = table[code_new].first_value; ctx->previous_code = code_new; @@ -362,7 +361,7 @@ lzw_result lzw_decode(struct lzw_ctx *ctx, * Note, in the case of "code not in table", the last entry of the * current code has already been placed on the stack above. */ while (code_out > clear_code) { - entry = table + code_out; + struct lzw_dictionary_entry *entry = table + code_out; *stack_pos++ = entry->last_value; code_out = entry->previous_entry; } |