From fa7045bf1c474288d5d2508ec6996cc2802c1b8f Mon Sep 17 00:00:00 2001 From: atxr Date: Mon, 19 Feb 2024 14:54:37 +0100 Subject: [PATCH] Add bitstream utility --- libmineziper/CMakeLists.txt | 2 + libmineziper/include/libmineziper_bitstream.h | 20 ++++ libmineziper/src/libmineziper_bitstream.c | 102 ++++++++++++++++++ 3 files changed, 124 insertions(+) create mode 100644 libmineziper/include/libmineziper_bitstream.h create mode 100644 libmineziper/src/libmineziper_bitstream.c diff --git a/libmineziper/CMakeLists.txt b/libmineziper/CMakeLists.txt index 1f0812c..350448e 100644 --- a/libmineziper/CMakeLists.txt +++ b/libmineziper/CMakeLists.txt @@ -5,11 +5,13 @@ set(libmineziper_STATIC_INCLUDE ${CMAKE_CURRENT_SOURCE_DIR}/include) set(libmineziper_SRC ${libmineziper_STATIC_SRC}/libmineziper.c ${libmineziper_STATIC_SRC}/libmineziper_zip.c + ${libmineziper_STATIC_SRC}/libmineziper_bitstream.c ) set(libmineziper_INCLUDE ${libmineziper_STATIC_INCLUDE}/libmineziper.h ${libmineziper_STATIC_INCLUDE}/libmineziper_zip.h + ${libmineziper_STATIC_INCLUDE}/libmineziper_bitstream.h ) # Create static library diff --git a/libmineziper/include/libmineziper_bitstream.h b/libmineziper/include/libmineziper_bitstream.h new file mode 100644 index 0000000..0553175 --- /dev/null +++ b/libmineziper/include/libmineziper_bitstream.h @@ -0,0 +1,20 @@ +#ifndef LIBMINEZIPER_BITSTREAM_H +#define LIBMINEZIPER_BITSTREAM_H + +typedef struct bitstream +{ + char *data; + int data_size; // size of 'data' array + int last_bit_offset; // last bit in the stream + + int current_data_offset; // position in 'data', i.e. + // data[current_data_offset] is current + // reading/writing byte + int current_bit_offset; // which bit we are currently reading/writing +} bitstream; + +char get_bits(bitstream *bs, unsigned int size); +void print_bits(int x, int size); +unsigned int reverse(unsigned int x, unsigned int numBits); + +#endif \ No newline at end of file diff --git a/libmineziper/src/libmineziper_bitstream.c b/libmineziper/src/libmineziper_bitstream.c new file mode 100644 index 0000000..5290e52 --- /dev/null +++ b/libmineziper/src/libmineziper_bitstream.c @@ -0,0 +1,102 @@ +#include "libmineziper_bitstream.h" + +#include + +char get_bits(bitstream *bs, unsigned int size) +{ + if (size > 32) + return -1; + + if (size == 0) + return 0; + + int out; + if (bs->current_bit_offset + size <= 8) + { + int mask = (1 << size) - 1; + mask <<= bs->current_bit_offset; + + out = bs->data[bs->current_data_offset] & mask; + + bs->current_bit_offset += size; + if (bs->current_bit_offset == 8) + { + bs->current_bit_offset = 0; + bs->current_data_offset++; + } + } + else + { + int diff = 8 - bs->current_bit_offset; + out = get_bits(bs, diff); + out += get_bits(bs, (bs->current_bit_offset + size) % 8); + } + + return out; +} + +unsigned int reverse(unsigned int x, unsigned int numBits) +{ + static const unsigned char reverse8[256] = { + 0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50, 0xD0, + 0x30, 0xB0, 0x70, 0xF0, 0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, + 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, 0x04, 0x84, 0x44, 0xC4, + 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, + 0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, 0x1C, 0x9C, 0x5C, 0xDC, + 0x3C, 0xBC, 0x7C, 0xFC, 0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, + 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, 0x0A, 0x8A, 0x4A, 0xCA, + 0x2A, 0xAA, 0x6A, 0xEA, 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA, + 0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, + 0x36, 0xB6, 0x76, 0xF6, 0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, + 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE, 0x01, 0x81, 0x41, 0xC1, + 0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1, + 0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99, 0x59, 0xD9, + 0x39, 0xB9, 0x79, 0xF9, 0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, + 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5, 0x0D, 0x8D, 0x4D, 0xCD, + 0x2D, 0xAD, 0x6D, 0xED, 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD, + 0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, + 0x33, 0xB3, 0x73, 0xF3, 0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, + 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB, 0x07, 0x87, 0x47, 0xC7, + 0x27, 0xA7, 0x67, 0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, + 0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, + 0x3F, 0xBF, 0x7F, 0xFF}; + + assert(x < (unsigned int) (1 << numBits)); + + // fast lookup if it fits in a byte + if (numBits == 8) + return reverse8[(unsigned char) x]; + + if (numBits < 8) + return reverse8[(unsigned char) x] >> (8 - numBits); + + // more than a byte, slower + unsigned int result = 0; + for (unsigned int i = 0; i < numBits; i++) + { + result <<= 1; + result |= x & 1; + x >>= 1; + } + return result; +} + +int get_bit_length(int x) +{ + int n = 0; + while (x != 0) + { + x >> 1; + n++; + } + return n; +} + +void print_bits(int x, int size) +{ + for (int i = size - 1; i >= 0; i--) + { + printf("%c", 0b1 & (x >> i) ? '1' : '0'); + } + printf("(%d,%d)", x, size); +} \ No newline at end of file