INI file parser

parser.c

#include <stdlib.h>
#include <stdio.h>

/*****************************************************************************
 * @function readValue extracts a string value from an INI file
 * @param f is a file opened for reading outside the function
 * @param section is the section name to look into
 * @param key is the key which value is required
 * @param buffer is a buffer to store the key value into
 * @note @param buffer should be long enough to store the value
 * @bug the function doesn't work with multi-line values
 ****************************************************************************/

int readValue(FILE *f, char *section, char *key, char *buffer) {
    rewind(f);
    char c = 0;
    int i;
    int newLine = 1;
    int inSectionName;
    int seekKey;
    int seekSection = 1;
    int readValue;
    do {
        do {
            do {
                c = fgetc(f);
                if (c == '\n') {
                    newLine = 1;
                }
            } while (newLine && seekSection && c != '[' && c != EOF);
            seekSection = 0;
            inSectionName = 1;
            i = 0;
            do {
                c = fgetc(f);
                if (c != section[i] && c != ']' && section[i]) {
                    seekSection = 1;
                }
                if (c == ']') {
                    inSectionName = 0;
                }
                if (c == '\n') {
                    newLine = 1;
                }
            } while (!seekSection && inSectionName && section[i++] && c != EOF);
            while (c != EOF && c != '\n') {
                c = fgetc(f);
            }
            newLine = 1;
        } while (c != EOF && seekSection);
        if (!seekSection) {
            do {
                seekKey = 0;
                i = 0;
                do {
                    c = fgetc(f);
                    if (c == '\n') {
                        newLine = 1;
                        i = 0;
                    }
                    while (newLine && (c == ' ' || c == '\t')) {
                        c = fgetc(f);
                    }
                    if (newLine && c == '[') {
                        seekSection = 1;
                        fseek(f, -1, SEEK_CUR);
                    }
                    newLine = 0;
                    if (!newLine && c != key[i++]) {
                        seekKey = 1;
                    }
                } while (!seekKey && !seekSection && key[i] && c != EOF);
                if (!seekSection && !seekKey) {
                    readValue = 0;
                    i = 0;
                    do {
                        c = fgetc(f);
                        if (c == '\n') {
                            newLine = 1;
                        }
                        if (c == '#') {         // inline comment
                            newLine = 1;
                            do {
                                c = fgetc(f);
                            } while (c != '\n');
                        }
                        if (readValue == 0 && (c == '=' || c == ':')) {
                            readValue = 1;
                        }
                        else if (readValue == 1 && c != ' ' && c != '\t') {
                            readValue = 2;
                        }
                        if (readValue == 2 && !newLine && c != EOF) {
                            *buffer = c;
                            ++buffer;
                            ++i;
                        }
                    } while (!newLine && c != EOF);
                    return i;
                }
            } while (!seekSection && c != EOF);
        }
        seekSection = 1;
    } while (c != EOF);
    return 0;
}

int main(int argc, char **argv) {
    const char fn[] = "sample.ini";
    char b[256] = {0};
    int r;
    FILE * f;
    if (f = fopen(fn, "r")) {
        r = readValue(f, "section", "key", b);
        printf("value: %s (%d characters)\n", b, r);
        fclose(f);
    }
    else {
        printf("%s `%s`\n", "failed to open", fn);
        return 1;
    }
    return 0;
}