C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_400/422_02/dosutil/diff.c

C/C++ Source or Header | 1994-03-20 | 4.8 KB | 224 lines

/*
 * Displays differences between two ASCII files
 *
 * Options:
 *    -d        = Inhibit display of differences
 *    -l        = Inhibit display of line numbers
 *    r=num    = Minimum # lines to re-syncronize
 *
 * Copyright 1988-1994 Dave Dunfield
 * All rights reserved.
 *
 * Permission granted for personal (non-commercial) use only.
 *
 * Compile command: cc diff -fop
 */
#include <stdio.h>

#define    LINE_SIZE    100        /* maximum size of input lines */
#define    MAX_DIFF    200        /* maximum number of different lines */

char ft1[MAX_DIFF][LINE_SIZE], ft2[MAX_DIFF][LINE_SIZE];

unsigned r1 = 0, r2 = 0, w1 = 0, w2 = 0, l1, l2;
unsigned resync = 2, diffs = 0;

char diff = -1, line = -1;

char *fn1, *fn2;
FILE *fp1, *fp2;

/*
 * Main program, compare files
 */
main(argc, argv)
    int argc;
    char *argv[];
{
    char *ptr;

    l2 = 0;
    for(l1 = 1; l1 < argc; ++l1) {
        ptr = argv[l1];
        switch((tolower(*ptr++) << 8) | tolower(*ptr++)) {
            case 'r=' :            /* minimum # lines to resync */
                resync = get_num(ptr);
                break;
            case '-d' :            /* inhibit display of differences */
                diff = 0;
                break;
            case '-l' :            /* inhibit display of line numbers */
                line = 0;
                break;
            default:            /* filename to compare */
                if(!(fp2 = fopen(fn2 = argv[l1], "r"))) {
                    fprintf(stderr, "%s: Unable to open\n", fn2);
                    exit(-1); }
                if(!l2++) {
                    fn1 = fn2;
                    fp1 = fp2; } } }

    if(l2 != 2) {
        fputs("\nUse: diff <file1> <file2> [-d -l r=#lines]\n\nCopyright 1988-1994 Dave Dunfield\nAll rights reserved.\n", stderr);
        exit(-1); }

    l1 = l2 = 1;
    for(;;) {
        fill_buffer();
        if((r1 == w1) || (r2 == w2)) {
            show_changed(w1, w2);
            if(diffs)
                fprintf(stdout,"%u differences.\n", diffs);
            else
                fprintf(stdout,"Files match exactly.\n");
            exit(diffs); }
        if(equal(ft1[r1], ft2[r2])) {
            r1 = (r1 + 1) % MAX_DIFF;
            r2 = (r2 + 1) % MAX_DIFF;
            ++l1; ++l2;
            continue; }
        scan_buffer(); }
}

/*
 * Fill up the buffer with lines from the input file
 */
fill_buffer()
{
    register int j1, j2;

    while((j1 = (w1 + 1) % MAX_DIFF) != r1) {
        if(!fgets(ft1[w1], LINE_SIZE, fp1))
            break;
        w1 = j1; }
    while((j2 = (w2 + 1) % MAX_DIFF) != r2) {
        if(!fgets(ft2[w2], LINE_SIZE, fp2))
            break;
        w2 = j2; }
}

/*
 * Scan the buffer looking for a pattern
 */
scan_buffer()
{
    int i, i1, i2, j1, j2;
    char flag;

    i1 = r1;
    i2 = r2;
    fill_buffer();
    do {        /* scan with this portion */
        j1 = i1;
        j2 = i2;
        do {
            flag = 0;
            if(j2 != w2) {        /* we can check this one */
                flag = -1;
                if(equal(ft1[i1], ft2[j2]) && (i=test_next(i1, j2))) {
                    show_changed(i1, j2);
                    r1 = (r1 + i) % MAX_DIFF;
                    r2 = (r2 + i) % MAX_DIFF;
                    l1 += i; l2 += i;
                    return; }
                j2 = (j2 + 1) % MAX_DIFF; }
            if(j1 != w1) {        /* we can check this one */
                flag = -1;
                if(equal(ft1[j1], ft2[i2]) && (i=test_next(j1, i2))) {
                    show_changed(j1, i2);
                    r1 = (r1 + i) % MAX_DIFF;
                    r2 = (r2 + i) % MAX_DIFF;
                    l1 += i; l2 += i;
                    return; }
                j1 = (j1 + 1) % MAX_DIFF; } }
        while(flag);
        if(i1 != w1) {        /* More lines in buffer */
            i1 = (i1 + 1) % MAX_DIFF;
            flag = -1; }
        if(i2 != w2) {        /* More lines in buffer */
            i2 = (i2 + 1) % MAX_DIFF;
            flag = -1; } }
    while(flag);

/* Cannot accept any more data into buffers, check for overflow */
    if((((w1 + 1) % MAX_DIFF) == r1) || (((w2 + 1) % MAX_DIFF) == r2)) {
        fprintf(stdout,"Differences to great at  %u < > %u\n", l1, l2);
        exit(-1); }
/* Buffers not full, must be end of file */
    show_changed(w1, w2);
}

/*
 * Test that the next "resync" entries match
 */
test_next(i1, i2)
    unsigned i1, i2;
{
    int i;

    for(i=1; i < resync; ++i) {
        i1 = (i1 + 1) % MAX_DIFF;
        i2 = (i2 + 1) % MAX_DIFF;
        if((i1 == w1) || (i2 == w2))
            return i;
        if(!equal(ft1[i1], ft2[i2]))
            return 0; }
    return i;
}

/*
 * Display the changed lines & reset read pointers
 */
show_changed(i1, i2)
    unsigned i1, i2;
{
    if((r1 != i1) || (r2 != i2)) {
        ++diffs;
        if(line)
            fprintf(stdout,"*** %s(%u) < > %s(%u) ***\n", fn1, l1, fn2, l2);
        while(r1 != i1) {
            ++l1;
            if(diff)
                fprintf(stdout,"<%s\n", ft1[r1]);
            r1 = (r1 + 1) % MAX_DIFF; }
        while(r2 != i2) {
            ++l2;
            if(diff)
                fprintf(stdout,">%s\n", ft2[r2]);
            r2 = (r2 + 1) % MAX_DIFF; } }
}

/*
 * Get a decimal number from the command line
 */
get_num(string)
    char *string;
{
    register unsigned value;
    register char chr;

    value = 0;
    while(isdigit(chr = *string++))
        value = (value * 10) + (chr - '0');

    if(chr) {
        fputs("DIFF: Invalid number\n", stderr);
        exit(-1); }

    return    value;
}

/*
 * Test for two strings equal
 */
equal(str1, str2)
    char *str1, *str2;
{
    register char c;

    while((c = *str1++) == *str2++) {
        if(!c)
            return 1; }
    return 0;
}