diff options
Diffstat (limited to 'libfonts.h')
| -rw-r--r-- | libfonts.h | 85 |
1 files changed, 84 insertions, 1 deletions
@@ -13,6 +13,13 @@ #define LIBFONTS_CONTEXT_VERSION 0 /** + * Target character index used to signify that the + * source character index is invalid or has not + * mapping to the target encoding + */ +#define LIBFONTS_UNDEFINED_CHAR (UINT32_C(0xFFFFFFFF)) + +/** * File name of file in font directories that is used * to create font aliases */ @@ -1866,7 +1873,6 @@ struct libfonts_encoding { * List of coded translation mappings */ struct libfonts_encoding_mapping *mappings; - /* TODO add functions for creating tables in either direction */ /** * The number of elements in `.mappings` @@ -1903,6 +1909,65 @@ struct libfonts_encoding { /** + * Lookup table for translating from one + * text encoding into another + */ +struct libfonts_transcoding_table { + /** + * Source character indices lower than + * this value should be rejected without + * looking in `.table` + */ + uint32_t first_valid; + + /** + * Source character indices higher than + * this value should be rejected without + * looking in `.table` + */ + uint32_t last_valid; + + /** + * See `.table` + */ + uint32_t offset; + + /** + * See `.table` + * + * If this value is 0, the source encoding uses one byte + * per character, otherwise it uses two bytes per character + */ + uint32_t multiplier; + + /** + * For a source character index `i`, the target character index is + * `.table[((i - .offset) >> 8) * .multiplier + ((i - .offset) & 0xFF)]` + * (`LIBFONTS_LOOKUP_TRANSCODING_TABLE` performs this lookup); + * however, if this value is `LIBFONTS_UNDEFINED_CHAR`, the + * character has no mapping: either `i` is an invalid character + * index in the source encoding, or the corresponding character + * does not exist in the target encoding + */ + uint32_t table[]; +}; + + +/** + * Converts a source character index to a target character index + * via a transcoding table + * + * @param TABLE:const struct libfonts_transcoding_table * The transcoding table + * @param I:uint32_t The source character index + * @return :uint32_t The target character index, or + * `LIBFONTS_UNDEFINED_CHAR` if there is no mapping + */ +#define LIBFONTS_LOOKUP_TRANSCODING_TABLE(TABLE, I)\ + ((TABLE)->table[(((uint32_t)(I) - (TABLE)->offset) >> 8) * (TABLE)->multiplier +\ + (((uint32_t)(I) - (TABLE)->offset) & 0xFF)]) + + +/** * Structure that can be used to spoof the * environment the library is executed in, * as well as the print warnings from the @@ -2158,6 +2223,24 @@ void libfonts_deallocate_encoding(struct libfonts_encoding *); */ int libfonts_parse_encoding_line(struct libfonts_encoding **, int *, const char *, char **, struct libfonts_context *); +/** + * Create a transcoding table + * + * @param encoding The source encoding + * @param mapping The index in `encoding->mappings` for the target encoding + * @return Transcoding table, deallocatable with free(3), or `NULL` on failure + * + * @throws ENOMEM Failed to allocate enough memory + * @throws EINVAL `encoding` is `NULL` + * @throws EINVAL `mapping` is equal to or greater than `encoding->nmappings` + * @throws EINVAL The contents of `encoding` is invalid + * @throws EINVAL One of the entries in the mapping has the + * `LIBFONTS_ENCODING_MAPPING_ENTRY_INDEX_TO_NAME` type + */ +struct libfonts_transcoding_table *libfonts_create_transcoding_table(const struct libfonts_encoding *, size_t); + +/* TODO add libfonts_create_reverse_transcoding_table */ + /** * Get the font a default font name aliases to |