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Diffstat (limited to 'libs/bitfield-c/src/bitfield/bitfield.h')
| -rw-r--r-- | libs/bitfield-c/src/bitfield/bitfield.h | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/libs/bitfield-c/src/bitfield/bitfield.h b/libs/bitfield-c/src/bitfield/bitfield.h new file mode 100644 index 00000000..df92639a --- /dev/null +++ b/libs/bitfield-c/src/bitfield/bitfield.h @@ -0,0 +1,220 @@ +#ifndef __BITFIELD_H__ +#define __BITFIELD_H__ + +#include <stdint.h> +#include <stdbool.h> + +#define NIBBLE_SIZE (CHAR_BIT / 2) + +#ifdef __cplusplus +extern "C" { +#endif + +/* Public: Reads a subset of bits into a uint64_t, right aligned so they may be + * interpreted as a number. + * + * source - the bytes in question. + * source_size - the number of bytes in the source. + * offset - the starting index of the bit field (beginning from 0). + * bit_count - the width of the bit field to extract. This must be less than or + * equal to 64. + * + * Bit fields are positioned according to big-endian bit layout and the data is + * swapped automatically as necessary depending on the compiled architecture. + * + * For example, the bit layout of the value "42" (i.e. 00101010 set at position + * 14 with length 6 is: + * + * 000000000000001010100000000000000000000000000000000000000000000 + * + * and the same value and position but with length 8 is: + * + * 000000000000000010101000000000000000000000000000000000000000000 + * + * Examples + * + * uint64_t value = get_bitfield(data, data_size, 2, 4); + * + * Returns the value of the requested bit field, right aligned in a uint64_t. + */ +uint64_t get_bitfield(const uint8_t source[], const uint8_t source_length, + const uint16_t offset, const uint16_t bit_count); + +/* Public: Return a single nibble from the byte array, with range checking. + * + * 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. + * + * 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. + * + * 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. + * + * 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). + * + * 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. + * + * For example: + * + * 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 + * + * Thanks to + * http://stackoverflow.com/questions/3534535/whats-a-time-efficient-algorithm-to-copy-unaligned-bit-arrays + * for the implementation of the algorithm. + * + * 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 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. + */ +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: 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. + * + * 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. + */ +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: Copy a range of bytes from one byte array to another. + * + * The source and destination do not have to be the same size (as long as the + * desitnation has enough room to fit the range). + * + * 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. + */ +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); + +/* Public: Set the a nibble in the given data array to the new value. + * + * nibble_index - the index of the nibble to retreive. The leftmost nibble is + * index 0. + * value - the value to set in the bit field. + * destination - the destination array. + * destination_length - the total length of the destination array in bytes, + * for range checking. + * + * Returns true if the bit_count is enough to fully represent the value, and + * false if it will not fit. + */ +bool set_nibble(const uint16_t nibble_index, const uint8_t value, + uint8_t* destination, const uint16_t destination_length); + +/* Public: Set the bit field in the given data array to the new value. + * + * value - the value to set in the bit field. + * offset - the starting index of the bit field (beginning from 0). + * bit_count - the number of bits to set in the data. + * destination - the destination array. + * destination_length - the total length of the destination array in bytes, + * for range checking. + * + * Returns true if the bit_count is enough to fully represent the value, and + * false if it will not fit. + */ +bool set_bitfield(const uint64_t value, const uint16_t offset, + const uint16_t bit_count, uint8_t destination[], + uint16_t destination_length); + +/* Public: Return a right aligned bitmask for a uint64_t. + * + * bit_count - the number of bits to mask, right aligned. + */ +uint64_t bitmask(const uint8_t bit_count); + +/* Private: + */ +uint16_t bits_to_bytes(uint32_t bits); + +/* Private: A union to assist swapping between uint64_t and a uint8_t array. + */ +typedef union { + uint64_t whole; + uint8_t bytes[sizeof(uint64_t)]; +} ArrayOrBytes; + +#ifdef __cplusplus +} +#endif + +#endif // __BITFIELD_H__ |