X-Git-Url: https://gerrit.automotivelinux.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fbitfield%2Fbitfield.h;h=ef04d9ca6aeab5fb7534bfd097339670bfa18b50;hb=4af52c415f1668fbd168da74d0aca903c592463f;hp=27766733fe37b5969a66d494a15a32278e950773;hpb=bc1baf25a0844861713829c0e9e69e4a2d447cc6;p=apps%2Fagl-service-can-low-level.git diff --git a/src/bitfield/bitfield.h b/src/bitfield/bitfield.h index 27766733..ef04d9ca 100644 --- a/src/bitfield/bitfield.h +++ b/src/bitfield/bitfield.h @@ -4,55 +4,144 @@ #include #include -/* Public: Reads a subset of bits from a byte array. +#define NIBBLE_SIZE (CHAR_BIT / 2) + +#ifdef __cplusplus +extern "C" { +#endif + +/* Public: Return a single nibble from the byte array, with range checking. * - * data - the bytes in question. - * startPos - the starting index of the bit field (beginning from 0). - * numBits - the width of the bit field to extract. - * bigEndian - if the data passed in is little endian, set this to false and it - * will be flipped before grabbing the bit field. + * source - the source byte array. + * source_length - the total length of the source array. + * nibble_index - the index of the nibble to retreive. The leftmost nibble is + * index 0. + * + * Returns the retreived nibble, right aligned in a uint8_t. + */ +uint8_t get_nibble(const uint8_t source[], const uint8_t source_length, + const uint8_t nibble_index); + +/* Public: Return a single byte from the byte array, with range checking. * - * Bit fields are positioned according to big-endian bit layout, but inside the - * bit field, values are represented as little-endian. Therefore, to get the bit - * field, we swap the overall byte order if bigEndian == false and - * use the value we find in the field (assuming the embedded platform is little - * endian). + * source - the source byte array. + * source_length - the total length of the source array. + * byte_index - the index of the byte to retreive. The leftmost byte is index 0. * - * For example, the bit layout of the value "42" (i.e. 00101010 set at position - * 14 with length 6 is: + * Returns the retreived byte. + */ +uint8_t get_byte(const uint8_t source[], const uint8_t source_length, + const uint8_t byte_index); + +/* Public: Copy a range of bits from one bit array to another. * - * 000000000000001010100000000000000000000000000000000000000000000 + * The range does not need to be byte aligned, and the source and destination do + * not have to be the same size (as long as the desitnation has enough room to + * fit the range). * - * and the same value and position but with length 8 is: + * A bit array with regards to this function always has the leftmost bit in byte + * 0, i.e. bit index is the leftmost bit of byte 0. Endianness does not matter. * - * 000000000000000010101000000000000000000000000000000000000000000 + * For example: * - * If the architecture where is code is running is little-endian, the input data - * will be swapped before grabbing the bit field. + * uint8_t source[4] = {0x11, 0x22, 0x33, 0x44}; + * uint8_t destination[4] = {0}; + * copy_bits(source, sizeof(source), 8, 8, destination, + * sizeof(destination), 0); + * // destination[0] == 0x22 + * // destination[1] == 0x0 + * // destination[2] == 0x0 + * // destination[3] == 0x0 * - * Examples + * Thanks to + * http://stackoverflow.com/questions/3534535/whats-a-time-efficient-algorithm-to-copy-unaligned-bit-arrays + * for the implementation of the algorithm. * - * uint64_t value = getBitField(data, 2, 4); + * source_origin - the source array. + * source_length - the total length of the source array in bytes, + * for range checking. + * source_offset - an offset in bits to start the copy from the source array. + * Specify 0 to start from source_origin. + * bit_count - the number of bits to copy. + * destination_origin - the destination array. + * desitnation_length - the total length of the destination array in bytes, + * for range checking. + * destination_offset - an offset in bits to start placing the copied range into + * the destination array. Specify 0 to start from the beginning of the + * destination. If you are copying a range not aligned on a byte, you + * probably want to set this to a positive offset to right the resulting + * bits in the destination. * - * Returns the value of the requested bit field. + * Returns true if the copy was successful and false if the range exceeded the + * size of the source or destination, or if the range size negative or 0. */ -uint64_t getBitField(uint64_t data, int startPos, int numBits, bool bigEndian); +bool copy_bits(const uint8_t* source_origin, const uint16_t source_length, + const uint16_t source_offset, uint16_t bit_count, + uint8_t* destination_origin, const uint16_t destination_length, + const uint16_t destination_offset); -/* Public: Set the bit field in the given data array to the new value. +/* Public: Copy a range of bits from one array to another, right aligning the + * result. + * + * This is mostly useful if you want to cast the result to an integer type + * instead of a byte array. * - * data - a byte array with size at least startPos + numBits. - * value - the value to set in the bit field. - * startPos - the starting index of the bit field (beginning from 0). + * For example: + * + * uint8_t source[4] = {0x11, 0x22, 0x33, 0x44}; + * uint8_t destination[4] = {0}; + * copy_bits_right_aligned(source, sizeof(source), 8, 8, destination, + * sizeof(destination)); + * // destination[0] == 0x0 + * // destination[1] == 0x0 + * // destination[2] == 0x0 + * // destination[3] == 0x22 + * + * int value = (int)destination; + * // value == 0x22 == 32 + * + * The arguments are the same as copy_bits, but without the destination_offset + * option - that's set automatically to right align the result. + * + * Returns true if the copy was successful and false if the range exceeded the + * size of the source or destination, or if the range size negative or 0. */ -void setBitField(uint64_t* data, uint64_t value, int startPos, int numBits); +bool copy_bits_right_aligned(const uint8_t source[], const uint16_t source_length, + const uint16_t offset, const uint16_t bit_count, + uint8_t* destination, const uint16_t destination_length); -/* Public: Retreive the nth byte out of 8 bytes in a uint64_t. +/* Public: Copy a range of bytes from one byte array to another. * - * source - the source data to retreive the byte from. - * byteNum - the index of the byte, starting at 0 and assuming big-endian order. + * The source and destination do not have to be the same size (as long as the + * desitnation has enough room to fit the range). * - * Returns the requested byte from the source bytes. + * source_origin - the source array. + * source_length - the total length of the source array in bytes, + * for range checking. + * source_offset - a byte offset to start the copy from the source array. + * Specify 0 to start from source_origin. + * byte_count - the number of bytes to copy. + * destination_origin - the destination array. + * desitnation_length - the total length of the destination array in bytes, + * for range checking. + * destination_offset - an offset in bytes to start placing the copied range into + * the destination array. Specify 0 to start from the beginning of the + * destination. + * + * Returns true if the copy was successful and false if the range exceeded the + * size of the source or destination, or if the range size negative or 0. */ -uint8_t nthByte(uint64_t source, int byteNum); +bool copy_bytes_right_aligned(const uint8_t source[], const uint16_t source_length, + const uint16_t offset, const uint16_t byte_count, + uint8_t* destination, const uint16_t destination_length); + +bool set_nibble(const uint16_t nibble_index, const uint8_t value, + uint8_t* destination, const uint16_t destination_length); + +uint16_t bits_to_bytes(uint32_t bits); + +#ifdef __cplusplus +} +#endif #endif // __BITFIELD_H__