/*
The MIT License (MIT)

Copyright © 2020-2025 pacman64

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
You can build this command-line app by running

cc -Wall -s -O2 -o ./bitdump ./bitdump.c
*/

#include <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>

#ifdef _WIN32
#include <windows.h>
#endif

// info is the multi-line help message
const char* info = ""
"bitdump [options...] [filenames...]\n"
"\n"
"Show all bits for all input bytes, starting each output line with the\n"
"leading byte's offset.\n"
"\n"
"\n"
"Options\n"
"\n"
"    -h, --h            show this help message\n"
"    -help, --help      aliases for option -h\n"
"";

// EMIT_CONST abstracts emitting string constants without their final null byte
#define EMIT_CONST(w, x) fwrite(x, sizeof(x) - 1, 1, w)

inline void write_bytes(FILE* w, const unsigned char* src, size_t len) {
    fwrite(src, len, 1, w);
}

/*
tlp = '(f"{bin(v)[2:]:>08}" for v in range(256))' | lineup 8 | gsub '\t' |
    tlp 'f"    \"{l}\""'
*/
const unsigned char lookup[256 * 8] = ""
    "0000000000000001000000100000001100000100000001010000011000000111"
    "0000100000001001000010100000101100001100000011010000111000001111"
    "0001000000010001000100100001001100010100000101010001011000010111"
    "0001100000011001000110100001101100011100000111010001111000011111"
    "0010000000100001001000100010001100100100001001010010011000100111"
    "0010100000101001001010100010101100101100001011010010111000101111"
    "0011000000110001001100100011001100110100001101010011011000110111"
    "0011100000111001001110100011101100111100001111010011111000111111"
    "0100000001000001010000100100001101000100010001010100011001000111"
    "0100100001001001010010100100101101001100010011010100111001001111"
    "0101000001010001010100100101001101010100010101010101011001010111"
    "0101100001011001010110100101101101011100010111010101111001011111"
    "0110000001100001011000100110001101100100011001010110011001100111"
    "0110100001101001011010100110101101101100011011010110111001101111"
    "0111000001110001011100100111001101110100011101010111011001110111"
    "0111100001111001011110100111101101111100011111010111111001111111"
    "1000000010000001100000101000001110000100100001011000011010000111"
    "1000100010001001100010101000101110001100100011011000111010001111"
    "1001000010010001100100101001001110010100100101011001011010010111"
    "1001100010011001100110101001101110011100100111011001111010011111"
    "1010000010100001101000101010001110100100101001011010011010100111"
    "1010100010101001101010101010101110101100101011011010111010101111"
    "1011000010110001101100101011001110110100101101011011011010110111"
    "1011100010111001101110101011101110111100101111011011111010111111"
    "1100000011000001110000101100001111000100110001011100011011000111"
    "1100100011001001110010101100101111001100110011011100111011001111"
    "1101000011010001110100101101001111010100110101011101011011010111"
    "1101100011011001110110101101101111011100110111011101111011011111"
    "1110000011100001111000101110001111100100111001011110011011100111"
    "1110100011101001111010101110101111101100111011011110111011101111"
    "1111000011110001111100101111001111110100111101011111011011110111"
    "1111100011111001111110101111101111111100111111011111111011111111"
    "";

// write_bin is faster than calling fprintf(w, "%08b", b): this matters
// because it's called for every input byte
inline void write_bin(FILE* w, unsigned char b) {
    const void* ptr = &lookup[8 * b];
    fwrite(ptr, 8, 1, w);
}

void write_decimal_uint(FILE* w, size_t n) {
    if (n < 1) {
        EMIT_CONST(w, "00000000");
        return;
    }

    size_t digits;
    // 20 is the most digits unsigned 64-bit ints can ever need
    unsigned char buf[24];
    for (digits = 0; n > 0; digits++, n /= 10) {
        buf[sizeof(buf) - 1 - digits] = (n % 10) + '0';
    }

    // left-pad the coming digits up to 8 chars
    if (digits < 8) {
        write_bytes(w, (unsigned char*)"00000000", 8 - digits);
    }

    // emit all digits
    unsigned char* start = buf + sizeof(buf) - digits;
    write_bytes(w, start, digits);
}

void write_hex_uint(FILE* w, size_t n) {
    if (n < 1) {
        EMIT_CONST(w, "00000000");
        return;
    }

    size_t digits;
    // 20 is the most digits unsigned 64-bit ints can ever need
    unsigned char buf[24];
    for (digits = 0; n > 0; digits += 2, n /= 256) {
        unsigned char b = n % 256;
        const char* hex_digits = "0123456789abcdef";
        buf[sizeof(buf) - 1 - digits - 1] = hex_digits[b >> 4];
        buf[sizeof(buf) - 1 - digits - 0] = hex_digits[b & 0x0f];
    }

    // left-pad the coming digits up to 8 chars
    if (digits < 8) {
        write_bytes(w, (unsigned char*)"00000000", 8 - digits);
    }

    // emit all digits
    unsigned char* start = buf + sizeof(buf) - digits;
    write_bytes(w, start, digits);
}

void decimal_offset(FILE* w, size_t offset) {
    write_decimal_uint(w, offset);
    putc(' ', w);
}

void hexadecimal_offset(FILE* w, size_t offset) {
    write_hex_uint(w, offset);
    putc(' ', w);
}

void no_offset(FILE*, size_t) {
}

// handle_reader shows all bytes read from the source given as colored hex
// values, showing offsets and ASCII symbols on the sides of each output line
void handle_reader(FILE* w, FILE* src, void (*start_row)(FILE*, size_t)) {
    const size_t bufcap = 32 * 1024;
    unsigned char buf[bufcap];
    size_t offset = 0;

    while (!feof(w)) {
        const size_t len = fread(&buf, sizeof(buf[0]), sizeof(buf), src);
        if (len < 1) {
            // assume input is over when no bytes were read
            if (offset > 0) {
                putc('\n', w);
            }
            break;
        }

        for (size_t i = 0; i < len; i++, offset++) {
            const size_t rem = offset % 8;
            if (rem == 0) {
                if (offset > 0) {
                    putc('\n', w);
                }
                start_row(w, offset);
            } else {
                putc(' ', w);
            }
            write_bin(w, buf[i]);
        }
    }
}

// handle_file handles data from the filename given; returns false only when
// the file can't be opened
bool handle_file(FILE* w, const char* path, void (*start_row)(FILE*, size_t)) {
    FILE* f = fopen(path, "rb");
    if (f == NULL) {
        // ensure currently-buffered/deferred output shows up right now: not
        // doing so may scramble results in the common case where stdout and
        // stderr are the same, thus confusing users
        putc('\n', w);

        fprintf(stderr, "\x1b[31mcan't open file named %s\x1b[0m\n", path);
        return false;
    }

    handle_reader(w, f, start_row);

    fclose(f);
    return true;
}

// is_help_option simplifies control-flow for func run
bool is_help_option(char* s) {
    return (s[0] == '-') && (
        strcmp(s, "-h") == 0 || strcmp(s, "-help") == 0 ||
        strcmp(s, "--h") == 0 || strcmp(s, "--help") == 0
    );
}

// run returns the number of errors
int run(int argc, char** argv, FILE* w) {
    size_t files = 0;
    size_t errors = 0;
    const void (*start_row)() = decimal_offset;

    // handle all filenames/options given
    for (size_t i = 1; i < argc && !feof(w); i++) {
        // a `-` filename stands for the standard input
        if (argv[i][0] == '-' && argv[i][1] == 0) {
            handle_reader(w, stdin, start_row);
            continue;
        }

        if (is_help_option(argv[i])) {
            // help option quits the app right away
            fprintf(stderr, "%s", info);
            return 0;
        }

        if (files > 0) {
            // put an empty line between adjacent outputs
            putc('\n', w);
        }

        if (!handle_file(w, argv[i], start_row)) {
            errors++;
        }
        files++;
    }

    // no filenames means use stdin as the only input
    if (files == 0) {
        handle_reader(w, stdin, start_row);
    }

    return errors;
}

int main(int argc, char** argv) {
#ifdef _WIN32
    setmode(fileno(stdin), O_BINARY);
    // ensure output lines end in LF instead of CRLF on windows
    setmode(fileno(stdout), O_BINARY);
    setmode(fileno(stderr), O_BINARY);
#endif

    return run(argc, argv, stdout) == 0 ? 0 : 1;
}