/*
 * Copyright 2007, Ingo Weinhold <bonefish@cs.tu-berlin.de>.
 * All rights reserved. Distributed under the terms of the MIT License.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>


void
write_string(int fd, const char* data)
{
        int len = strlen(data);
        if (len == 0)
                return;

        ssize_t written = write(fd, data, len);
        if (written < 0) {
                fprintf(stderr, "Error: Failed to write to output file: %s\n",
                        strerror(errno));
                exit(1);
        }
}


int
main(int argc, const char* const* argv)
{
        if (argc != 5) {
                fprintf(stderr,
                        "Usage: %s <data var name> <size var name> <input> <output>\n",
                        argv[0]);
                exit(1);
        }
        const char* dataVarName = argv[1];
        const char* sizeVarName = argv[2];
        const char* inFileName = argv[3];
        const char* outFileName = argv[4];

        // open files
        int inFD = open(inFileName, O_RDONLY);
        if (inFD < 0) {
                fprintf(stderr, "Error: Failed to open input file \"%s\": %s\n",
                        inFileName, strerror(errno));
                exit(1);
        }

        int outFD = open(outFileName, O_WRONLY | O_CREAT | O_TRUNC,
                S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
        if (outFD < 0) {
                fprintf(stderr, "Error: Failed to open output file \"%s\": %s\n",
                        outFileName, strerror(errno));
                exit(1);
        }

        const int kCharsPerLine = 15;
        const int kBufferSize = 16 * 1024;
        unsigned char buffer[kBufferSize];
        char lineBuffer[128];

        sprintf(lineBuffer, "#include <stddef.h>\n");
        write_string(outFD, lineBuffer);
        sprintf(lineBuffer, "const unsigned char %s[] = {\n", dataVarName);
        write_string(outFD, lineBuffer);

        off_t offset = 0;
        char* lineBufferEnd = lineBuffer;
        *lineBufferEnd = '\0';
        while (true) {
                // read a buffer
                ssize_t bytesRead = read(inFD, buffer, kBufferSize);
                if (bytesRead < 0) {
                        fprintf(stderr, "Error: Failed to read from input file: %s\n",
                                strerror(errno));
                        exit(1);
                }
                if (bytesRead == 0)
                        break;

                // write lines
                for (int i = 0; i < bytesRead; i++, offset++) {
                        if (offset % kCharsPerLine == 0) {
                                if (offset > 0) {
                                        // line is full -- flush it
                                        strcpy(lineBufferEnd, ",\n");
                                        write_string(outFD, lineBuffer);
                                        lineBufferEnd = lineBuffer;
                                        *lineBufferEnd = '\0';
                                }

                                sprintf(lineBufferEnd, "\t%u", (unsigned)buffer[i]);
                        } else
                                sprintf(lineBufferEnd, ", %u", (unsigned)buffer[i]);

                        lineBufferEnd += strlen(lineBufferEnd);
                }
        }

        // flush the line buffer
        if (lineBufferEnd != lineBuffer) {
                strcpy(lineBufferEnd, ",\n");
                write_string(outFD, lineBuffer);
        }

        // close the braces and write the size variable
        sprintf(lineBuffer, "};\nconst size_t %s = sizeof(%s);\n", sizeVarName,
                dataVarName);
        write_string(outFD, lineBuffer);

        close(inFD);
        close(outFD);

        return 0;
}