/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */


/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <fatal.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <wait.h>

#define ONSIG   16

/*
 *      This program segments two files into pieces of <= seglim lines
 *      (which is passed as a third argument or defaulted to some number)
 *      and then executes diff upon the pieces. The output of
 *      'diff' is then processed to make it look as if 'diff' had
 *      processed the files whole. The reason for all this is that seglim
 *      is a reasonable upper limit on the size of files that diff can
 *      process.
 *      NOTE -- by segmenting the files in this manner, it cannot be
 *      guaranteed that the 'diffing' of the segments will generate
 *      a minimal set of differences.
 *      This process is most definitely not equivalent to 'diffing'
 *      the files whole, assuming 'diff' could handle such large files.
 *
 *      'diff' is executed by a child process, generated by forking,
 *      and communicates with this program through pipes.
 */

static char Error[128];

static int seglim;      /* limit of size of file segment to be generated */

static char diff[]  =  "/usr/bin/diff";
static char tempskel[] = "/tmp/bdXXXXXX"; /* used to generate temp file names */
static char tempfile[32];
static char otmp[32], ntmp[32];
static int      fflags;
static int      fatal_num = 1;          /* exit number for fatal exit */
static offset_t linenum;
static size_t obufsiz, nbufsiz, dbufsiz;
static char *readline(char **, size_t *, FILE *);
static void addgen(char **, size_t *, FILE *);
static void delgen(char **, size_t *, FILE *);
static void fixnum(char *);
static void fatal(char *);
static void setsig(void);
static void setsig1(int);
static char *satoi(char *, offset_t *);
static FILE *maket(char *);

static char *prognam;

int
main(int argc, char *argv[])
{
        FILE *poldfile, *pnewfile;
        char *oline, *nline, *diffline;
        char *olp, *nlp, *dp;
        int otcnt, ntcnt;
        pid_t i;
        int pfd[2];
        FILE *poldtemp, *pnewtemp, *pipeinp;
        int status;

        prognam = argv[0];
        /*
         * Set flags for 'fatal' so that it will clean up,
         * produce a message, and terminate.
         */
        fflags = FTLMSG | FTLCLN | FTLEXIT;

        setsig();

        if (argc < 3 || argc > 5)
                fatal("arg count");

        if (strcmp(argv[1], "-") == 0 && strcmp(argv[2], "-") == 0)
                fatal("both files standard input");
        if (strcmp(argv[1], "-") == 0)
                poldfile = stdin;
        else
                if ((poldfile = fopen(argv[1], "r")) == NULL) {
                        (void) snprintf(Error, sizeof (Error),
                                "Can not open '%s'", argv[1]);
                        fatal(Error);
                }
        if (strcmp(argv[2], "-") == 0)
                pnewfile = stdin;
        else
                if ((pnewfile = fopen(argv[2], "r")) == NULL) {
                        (void) snprintf(Error, sizeof (Error),
                                "Can not open '%s'", argv[2]);
                        fatal(Error);
                }

        seglim = 3500;

        if (argc > 3) {
                if (argv[3][0] == '-' && argv[3][1] == 's')
                        fflags &= ~FTLMSG;
                else {
                        if ((seglim = atoi(argv[3])) == 0)
                                fatal("non-numeric limit");
                        if (argc == 5 && argv[4][0] == '-' &&
                                        argv[4][1] == 's')
                                fflags &= ~FTLMSG;
                }
        }

        linenum = 0;

        /* Allocate the buffers and initialize their lengths */

        obufsiz = BUFSIZ;
        nbufsiz = BUFSIZ;
        dbufsiz = BUFSIZ;

        if ((oline = (char *)malloc(obufsiz)) == NULL ||
            (nline = (char *)malloc(nbufsiz)) == NULL ||
            (diffline = (char *)malloc(dbufsiz)) == NULL)
                fatal("Out of memory");

        /*
         * The following while-loop will prevent any lines
         * common to the beginning of both files from being
         * sent to 'diff'. Since the running time of 'diff' is
         * non-linear, this will help improve performance.
         * If, during this process, both files reach EOF, then
         * the files are equal and the program will terminate.
         * If either file reaches EOF before the other, the
         * program will generate the appropriate 'diff' output
         * itself, since this can be easily determined and will
         * avoid executing 'diff' completely.
         */
        for (;;) {
                olp = readline(&oline, &obufsiz, poldfile);
                nlp = readline(&nline, &nbufsiz, pnewfile);

                if (!olp && !nlp)       /* EOF found on both:  files equal */
                        return (0);

                if (!olp) {
                        /*
                         * The entire old file is a prefix of the
                         * new file. Generate the appropriate "append"
                         * 'diff'-like output, which is of the form:
                         *              nan, n
                         * where 'n' represents a line-number.
                         */
                        addgen(&nline, &nbufsiz, pnewfile);
                }

                if (!nlp) {
                        /*
                         * The entire new file is a prefix of the
                         * old file. Generate the appropriate "delete"
                         * 'diff'-like output, which is of the form:
                         *              n, ndn
                         * where 'n' represents a line-number.
                         */
                        delgen(&oline, &obufsiz, poldfile);
                }

                if (strcmp(olp, nlp) == 0)
                        linenum++;
                else
                        break;
        }

        /*
         * Here, first 'linenum' lines are equal.
         * The following while-loop segments both files into
         * seglim segments, forks and executes 'diff' on the
         * segments, and processes the resulting output of
         * 'diff', which is read from a pipe.
         */
        for (;;) {
                /* If both files are at EOF, everything is done. */
                if (!olp && !nlp)       /* finished */
                        return (0);

                if (!olp) {
                        /*
                         * Generate appropriate "append"
                         * output without executing 'diff'.
                         */
                        addgen(&nline, &nbufsiz, pnewfile);
                }

                if (!nlp) {
                        /*
                         * Generate appropriate "delete"
                         * output without executing 'diff'.
                         */
                        delgen(&oline, &obufsiz, poldfile);
                }

                /*
                 * Create a temporary file to hold a segment
                 * from the old file, and write it.
                 */
                poldtemp = maket(otmp);
                otcnt = 0;
                while (olp && otcnt < seglim) {
                        (void) fputs(oline, poldtemp);
                        if (ferror(poldtemp) != 0) {
                                fflags |= FTLMSG;
                                fatal("Can not write to temporary file");
                        }
                        olp = readline(&oline, &obufsiz, poldfile);
                        otcnt++;
                }
                (void) fclose(poldtemp);

                /*
                 * Create a temporary file to hold a segment
                 * from the new file, and write it.
                 */
                pnewtemp = maket(ntmp);
                ntcnt = 0;
                while (nlp && ntcnt < seglim) {
                        (void) fputs(nline, pnewtemp);
                        if (ferror(pnewtemp) != 0) {
                                fflags |= FTLMSG;
                                fatal("Can not write to temporary file");
                        }
                        nlp = readline(&nline, &nbufsiz, pnewfile);
                        ntcnt++;
                }
                (void) fclose(pnewtemp);

                /* Create pipes and fork.  */
                if ((pipe(pfd)) == -1)
                        fatal("Can not create pipe");
                if ((i = fork()) < (pid_t)0) {
                        (void) close(pfd[0]);
                        (void) close(pfd[1]);
                        fatal("Can not fork, try again");
                } else if (i == (pid_t)0) {     /* child process */
                        (void) close(pfd[0]);
                        (void) close(1);
                        (void) dup(pfd[1]);
                        (void) close(pfd[1]);

                        /* Execute 'diff' on the segment files. */
                        (void) execlp(diff, diff, otmp, ntmp, 0);

                        /*
                         * Exit code here must be > 1.
                         * Parent process treats exit code of 1 from the child
                         * as non-error because the child process "diff" exits
                         * with a status of 1 when a difference is encountered.
                         * The error here is a true error--the parent process
                         * needs to detect it and exit with a non-zero status.
                         */
                        (void) close(1);
                        (void) snprintf(Error, sizeof (Error),
                            "Can not execute '%s'", diff);
                        fatal_num = 2;
                        fatal(Error);
                } else {                        /* parent process */
                        (void) close(pfd[1]);
                        pipeinp = fdopen(pfd[0], "r");

                        /* Process 'diff' output. */
                        while ((dp = readline(&diffline, &dbufsiz, pipeinp))) {
                                if (isdigit(*dp))
                                        fixnum(diffline);
                                else
                                        (void) printf("%s", diffline);
                        }

                        (void) fclose(pipeinp);

                        /* EOF on pipe. */
                        (void) wait(&status);
                        if (status&~0x100) {
                                (void) snprintf(Error, sizeof (Error),
                                    "'%s' failed", diff);
                                fatal(Error);
                        }
                }
                linenum += seglim;

                /* Remove temporary files. */
                (void) unlink(otmp);
                (void) unlink(ntmp);
        }
}

/* Routine to save remainder of a file. */
static void
saverest(char **linep, size_t *bufsizp, FILE *iptr)
{
        char *lp;
        FILE *temptr;

        temptr = maket(tempfile);

        lp = *linep;

        while (lp) {
                (void) fputs(*linep, temptr);
                linenum++;
                lp = readline(linep, bufsizp, iptr);
        }
        (void) fclose(temptr);
}

/* Routine to write out data saved by 'saverest' and to remove the file. */
static void
putsave(char **linep, size_t *bufsizp, char type)
{
        FILE *temptr;

        if ((temptr = fopen(tempfile, "r")) == NULL) {
                (void) snprintf(Error, sizeof (Error),
                    "Can not open tempfile ('%s')", tempfile); fatal(Error);
        }

        while (readline(linep, bufsizp, temptr))
                (void) printf("%c %s", type, *linep);

        (void) fclose(temptr);

        (void) unlink(tempfile);
}

static void
fixnum(char *lp)
{
        offset_t num;

        while (*lp) {
                switch (*lp) {

                case 'a':
                case 'c':
                case 'd':
                case ',':
                case '\n':
                        (void) printf("%c", *lp);
                        lp++;
                        break;

                default:
                        lp = satoi(lp, &num);
                        num += linenum;
                        (void) printf("%lld", num);
                }
        }
}

static void
addgen(char **lpp, size_t *bufsizp, FILE *fp)
{
        offset_t oldline;
        (void) printf("%llda%lld", linenum, linenum+1);

        /* Save lines of new file. */
        oldline = linenum + 1;
        saverest(lpp, bufsizp, fp);

        if (oldline < linenum)
                (void) printf(",%lld\n", linenum);
        else
                (void) printf("\n");

        /* Output saved lines, as 'diff' would. */
        putsave(lpp, bufsizp, '>');

        exit(0);
}

static void
delgen(char **lpp, size_t *bufsizp, FILE *fp)
{
        offset_t savenum;

        (void) printf("%lld", linenum+1);
        savenum = linenum;

        /* Save lines of old file. */
        saverest(lpp, bufsizp, fp);

        if (savenum +1 != linenum)
                (void) printf(",%lldd%lld\n", linenum, savenum);
        else
                (void) printf("d%lld\n", savenum);

        /* Output saved lines, as 'diff' would.  */
        putsave(lpp, bufsizp, '<');

        exit(0);
}

static void
clean_up()
{
        (void) unlink(tempfile);
        (void) unlink(otmp);
        (void) unlink(ntmp);
}

static FILE *
maket(char *file)
{
        FILE *iop;
        int fd;

        (void) strcpy(file, tempskel);
        if ((fd = mkstemp(file)) == -1 ||
                (iop = fdopen(fd, "w+")) == NULL) {
                (void) snprintf(Error, sizeof (Error),
                    "Can not open/create temp file ('%s')", file);
                fatal(Error);
        }
        return (iop);
}

static void
fatal(char *msg)
/*
 *      General purpose error handler.
 *
 *      The argument to fatal is a pointer to an error message string.
 *      The action of this routine is driven completely from
 *      the "fflags" global word (see <fatal.h>).
 *
 *      The FTLMSG bit controls the writing of the error
 *      message on file descriptor 2.  A newline is written
 *      after the user supplied message.
 *
 *      If the FTLCLN bit is on, clean_up is called.
 */
{
        if (fflags & FTLMSG)
                (void) fprintf(stderr, "%s: %s\n", prognam, msg);
        if (fflags & FTLCLN)
                clean_up();
        if (fflags & FTLEXIT)
                exit(fatal_num);
}

static void
setsig()
/*
 *      General-purpose signal setting routine.
 *      All non-ignored, non-caught signals are caught.
 *      If a signal other than hangup, interrupt, or quit is caught,
 *      a "user-oriented" message is printed on file descriptor 2.
 *      If hangup, interrupt or quit is caught, that signal
 *      is set to ignore.
 *      Termination is like that of "fatal",
 *      via "clean_up()"
 */
{
        void (*act)(int);
        int j;

        for (j = 1; j < ONSIG; j++) {
                act = signal(j, setsig1);
                if (act == SIG_ERR)
                        continue;
                if (act == SIG_DFL)
                        continue;
                (void) signal(j, act);
        }
}

static void
setsig1(int sig)
{

        (void) signal(sig, SIG_IGN);
        clean_up();
        exit(1);
}

static char *
satoi(char *p, offset_t *ip)
{
        offset_t sum;

        sum = 0;
        while (isdigit(*p))
                sum = sum * 10 + (*p++ - '0');
        *ip = sum;
        return (p);
}

/*
 * Read a line of data from a file.  If the current buffer is not large enough
 * to contain the line, double the size of the buffer and continue reading.
 * Loop until either the entire line is read or until there is no more space
 * to be malloc'd.
 */

static char *
readline(char **bufferp, size_t *bufsizp, FILE *filep)
{
        char *bufp;
        size_t newsize;         /* number of bytes to make buffer */
        size_t oldsize;

        (*bufferp)[*bufsizp - 1] = '\t'; /* arbitrary non-zero character */
        (*bufferp)[*bufsizp - 2] = ' '; /* arbitrary non-newline char */
        bufp = fgets(*bufferp, *bufsizp, filep);
        if (bufp == NULL)
                return (bufp);
        while ((*bufferp)[*bufsizp -1] == '\0' &&
            (*bufferp)[*bufsizp - 2] != '\n' &&
            strlen(*bufferp) == *bufsizp - 1) {
                newsize = 2 * (*bufsizp);
                bufp = (char *)realloc((void *)*bufferp, newsize);
                if (bufp == NULL)
                        fatal("Out of memory");
                oldsize = *bufsizp;
                *bufsizp = newsize;
                *bufferp = bufp;
                (*bufferp)[*bufsizp - 1] = '\t';
                (*bufferp)[*bufsizp - 2] = ' ';
                bufp = fgets(*bufferp + oldsize -1, oldsize + 1, filep);
                if (bufp == NULL) {
                        if (filep->_flag & _IOEOF) {
                                bufp = *bufferp;
                                break;
                        } else
                                fatal("Read error");
                } else
                        bufp = *bufferp;
        }
        return (bufp);
}