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+ 9AB0950EFF37136222DC461537F8448EBC36DFF595E77AF294E48F9142657ED6DA78D72C232ECC890E28BA75A2160D7AB3A09E1A7AA61C50AC95C7A747EF2B7A
vtools/src/io.c

(0 . 0)(1 . 596)

#include "diff.h"
#include <cmpbuf.h>
#include <xalloc.h>
#include <string.h>
#include <limits.h>
#include <stdlib.h>

/* Rotate an unsigned value to the left.  */
#define ROL(v, n) ((v) << (n) | (v) >> (sizeof (v) * CHAR_BIT - (n)))

/* Given a hash value and a new character, return a new hash
   value.  */
#define HASH(h, c) ((c) + ROL (h, 7))

/* The type of a hash value.  */
typedef size_t hash_value;

/* Lines are put into equivalence classes of lines that match in
   |lines_differ|.  Each equivalence class is represented by one of
   these structures, but only while the classes are being computed.
   Afterward, each class is represented by a number.  */
struct equivclass {
    lin next;        /* Next item in this bucket.  */
    hash_value hash;    /* Hash of lines in this class.  */
    char const *line;    /* A line that fits this class.  */
    size_t length;    /* That line's length, not counting its newline.  */
};

/* Hash-table: array of buckets, each being a chain of equivalence
   classes.  |buckets[-1]| is reserved for incomplete lines.  */
static lin *buckets;

/* Number of buckets in the hash table array, not counting
   |buckets[-1]|.  */
static size_t nbuckets;

/* Array in which the equivalence classes are allocated.  The
   bucket-chains go through the elements in this array.  The number of
   an equivalence class is its index in this array.  */
static struct equivclass *equivs;

/* Index of first free element in the array |equivs|.  */
static lin equivs_index;

/* Number of elements allocated in the array |equivs|.  */
static lin equivs_alloc;

/* Read a block of data into a file buffer, checking for EOF and
   error.  */

void
file_block_read(struct file_data *current, size_t size) {
    if (size && !current->eof) {
        size_t s = block_read(current->desc,
                              FILE_BUFFER (current) + current->buffered, size);
        if (s == SIZE_MAX)
            pfatal_with_name(current->name);

        current->buffered += s;
        current->eof = s < size;
    }
}

/* Check for binary files and compare them for exact identity.  */

/* Return 1 if |buf| contains a non text character.  |size| is the
   number of characters in |buf|.  */

#define binary_file_p(buf, size) (memchr (buf, 0, size) != 0)

/* Get ready to read the current file.  Return nonzero if |skip_test|
   is zero, and if it appears to be a binary file.  */

static bool
sip(struct file_data *current, bool skip_test) {
    /* If we have a nonexistent file at this stage, treat it as
       empty.  */
    if (current->desc < 0) {
        /* Leave room for a sentinel.  */
        current->bufsize = sizeof(word);
        current->buffer = xmalloc(current->bufsize);
    } else {
        current->bufsize = buffer_lcm(sizeof(word),
                                      STAT_BLOCKSIZE (current->stat),
                                      PTRDIFF_MAX - 2 * sizeof(word));
        current->buffer = xmalloc(current->bufsize);

        if (!skip_test) {
            /* Check first part of file to see if it's a binary file.  */

            off_t buffered;
            file_block_read(current, current->bufsize);
            buffered = current->buffered;
            return binary_file_p (current->buffer, buffered);
        }
    }

    current->buffered = 0;
    current->eof = false;
    return false;
}

/* Slurp the rest of the current file completely into memory.  */

static void
slurp(struct file_data *current) {
    size_t cc;

    if (current->desc < 0) {
        /* The file is nonexistent.  */
        return;
    }

    if (S_ISREG (current->stat.st_mode)) {
        /* It's a regular file; slurp in the rest all at once.  */

        /* Get the size out of the stat block.  Allocate just enough
       room for appended newline plus word sentinel, plus
       word-alignment since we want the buffer word-aligned.  */
        size_t file_size = current->stat.st_size;
        cc = file_size + 2 * sizeof(word) - file_size % sizeof(word);
        if (file_size != current->stat.st_size || cc < file_size
            || PTRDIFF_MAX <= cc)
            xalloc_die();

        if (current->bufsize < cc) {
            current->bufsize = cc;
            current->buffer = xrealloc(current->buffer, cc);
        }

        /* Try to read at least 1 more byte than the size indicates,
       to detect whether the file is growing.  This is a nicety for
       users who run 'diff' on files while they are changing.  */

        if (current->buffered <= file_size) {
            file_block_read(current, file_size + 1 - current->buffered);
            if (current->buffered <= file_size)
                return;
        }
    }

    /* It's not a regular file, or it's a growing regular file; read
       it, growing the buffer as needed.  */

    file_block_read(current, current->bufsize - current->buffered);

    if (current->buffered) {
        while (current->buffered == current->bufsize) {
            if (PTRDIFF_MAX / 2 - sizeof(word) < current->bufsize)
                xalloc_die();
            current->bufsize *= 2;
            current->buffer = xrealloc(current->buffer, current->bufsize);
            file_block_read(current, current->bufsize - current->buffered);
        }

        /* Allocate just enough room for appended newline plus word
       sentinel, plus word-alignment.  */
        cc = current->buffered + 2 * sizeof(word);
        current->bufsize = cc - cc % sizeof(word);
        current->buffer = xrealloc(current->buffer, current->bufsize);
    }
}

/* Split the file into lines, simultaneously computing the equivalence
   class for each line.  */

static void
find_and_hash_each_line(struct file_data *current) {
    char const *p = current->prefix_end;
    lin i, *bucket;
    size_t length;

    /* Cache often-used quantities in local variables to help the compiler.  */
    char const **linbuf = current->linbuf;
    lin alloc_lines = current->alloc_lines;
    lin line = 0;
    lin linbuf_base = current->linbuf_base;
    lin *cureqs = xmalloc(alloc_lines * sizeof *cureqs);
    struct equivclass *eqs = equivs;
    lin eqs_index = equivs_index;
    lin eqs_alloc = equivs_alloc;
    char const *suffix_begin = current->suffix_begin;
    char const *bufend = FILE_BUFFER (current) + current->buffered;


    while (p < suffix_begin) {
        char const *ip = p;
        hash_value h = 0;
        unsigned char c;

        /* Hash this line until we find a newline.  */
        while ((c = *p++) != '\n')
            h = HASH (h, c);

        bucket = &buckets[h % nbuckets];
        length = p - ip - 1;

        for (i = *bucket;; i = eqs[i].next)
            if (!i) {
                /* Create a new equivalence class in this bucket.  */
                i = eqs_index++;
                if (i == eqs_alloc) {
                    if (PTRDIFF_MAX / (2 * sizeof *eqs) <= eqs_alloc)
                        xalloc_die();
                    eqs_alloc *= 2;
                    eqs = xrealloc(eqs, eqs_alloc * sizeof *eqs);
                }
                eqs[i].next = *bucket;
                eqs[i].hash = h;
                eqs[i].line = ip;
                eqs[i].length = length;
                *bucket = i;
                break;
            } else if (eqs[i].hash == h) {
                char const *eqline = eqs[i].line;

                /* Reuse existing class if |lines_differ| reports the
                   lines equal.  */
                if (eqs[i].length == length) {
                    /* Reuse existing equivalence class if the lines
                       are identical.  This detects the common case of
                       exact identity faster than |lines_differ|
                       would.  */
                    if (memcmp(eqline, ip, length) == 0)
                        break;
                    continue;
                } else
                    continue;
            }

        /* Maybe increase the size of the line table.  */
        if (line == alloc_lines) {
            /* Double |(alloc_lines - linbuf_base)| by adding to
               |alloc_lines|.  */
            if (PTRDIFF_MAX / 3 <= alloc_lines
                || PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
                || PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
                xalloc_die();
            alloc_lines = 2 * alloc_lines - linbuf_base;
            cureqs = xrealloc(cureqs, alloc_lines * sizeof *cureqs);
            linbuf += linbuf_base;
            linbuf = xrealloc(linbuf,
                              (alloc_lines - linbuf_base) * sizeof *linbuf);
            linbuf -= linbuf_base;
        }
        linbuf[line] = ip;
        cureqs[line] = i;
        ++line;
    }

    current->buffered_lines = line;

    for (i = 0;; i++) {
        /* Record the line start for lines in the suffix that we care
       about.  Record one more line start than lines, so that we can
       compute the length of any buffered line.  */
        if (line == alloc_lines) {
            /* Double |(alloc_lines - linbuf_base)| by adding to
               |alloc_lines|.  */
            if (PTRDIFF_MAX / 3 <= alloc_lines
                || PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
                || PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
                xalloc_die();
            alloc_lines = 2 * alloc_lines - linbuf_base;
            linbuf += linbuf_base;
            linbuf = xrealloc(linbuf,
                              (alloc_lines - linbuf_base) * sizeof *linbuf);
            linbuf -= linbuf_base;
        }
        linbuf[line] = p;

        if (p == bufend) {
            /* If the last line is incomplete and we do not silently
               complete lines, don't count its appended newline.  */
            if (current->missing_newline && false) /* our output style not robust */
                linbuf[line]--;
            break;
        }

        line++;

        while (*p++ != '\n')
            continue;
    }

    /* Done with cache in local variables.  */
    current->linbuf = linbuf;
    current->valid_lines = line;
    current->alloc_lines = alloc_lines;
    current->equivs = cureqs;
    equivs = eqs;
    equivs_alloc = eqs_alloc;
    equivs_index = eqs_index;
}

/* Prepare the text.  Make sure the text end is initialized.  Make
   sure text ends in a newline, but remember that we had to add one.
   Strip trailing CRs, if that was requested.  */

static void
prepare_text(struct file_data *current) {
    size_t buffered = current->buffered;
    char *p = FILE_BUFFER (current);

    if (buffered == 0 || p[buffered - 1] == '\n')
        current->missing_newline = false;
    else {
        p[buffered++] = '\n';
        current->missing_newline = true;
    }

    if (!p)
        return;

    /* Don't use uninitialized storage when planting or using sentinels.  */
    memset (p + buffered, 0, sizeof(word));

    current->buffered = buffered;
}

/* We have found |n| lines in a buffer of size |s|; guess the
   proportionate number of lines that will be found in a buffer of
   size |t|.  However, do not guess a number of lines so large that
   the resulting line table might cause overflow in size
   calculations.  */
static lin
guess_lines(lin n, size_t s, size_t t) {
    size_t guessed_bytes_per_line = n < 10 ? 32 : s / (n - 1);
    lin guessed_lines = MAX (1, t / guessed_bytes_per_line);
    return MIN (guessed_lines, PTRDIFF_MAX / (2 * sizeof(char *) + 1) - 5) + 5;
}

/* Given a vector of two |file_data| objects, find the identical
   prefixes and suffixes of each object.  */

static void
find_identical_ends(struct file_data filevec[]) {
    word *w0, *w1;
    char *p0, *p1, *buffer0, *buffer1;
    char const *end0, *beg0;
    char const **linbuf0, **linbuf1;
    lin i, lines;
    size_t n0, n1;
    lin alloc_lines0, alloc_lines1;
    lin buffered_prefix, prefix_count, prefix_mask;
    lin middle_guess, suffix_guess;

    slurp(&filevec[0]);
    prepare_text(&filevec[0]);
    if (filevec[0].desc != filevec[1].desc) {
        slurp(&filevec[1]);
        prepare_text(&filevec[1]);
    } else {
        filevec[1].buffer = filevec[0].buffer;
        filevec[1].bufsize = filevec[0].bufsize;
        filevec[1].buffered = filevec[0].buffered;
        filevec[1].missing_newline = filevec[0].missing_newline;
    }

    /* Find identical prefix.  */

    w0 = filevec[0].buffer;
    w1 = filevec[1].buffer;
    p0 = buffer0 = (char *) w0;
    p1 = buffer1 = (char *) w1;
    n0 = filevec[0].buffered;
    n1 = filevec[1].buffered;

    if (p0 == p1)
        /* The buffers are the same; sentinels won't work.  */
        p0 = p1 += n1;
    else {
        /* Insert end sentinels, in this case characters that are
       guaranteed to make the equality test false, and thus terminate
       the loop.  */

        if (n0 < n1)
            p0[n0] = ~p1[n0];
        else
            p1[n1] = ~p0[n1];

        /* Loop until first mismatch, or to the sentinel
           characters.  */

        /* Compare a word at a time for speed.  */
        while (*w0 == *w1)
            w0++, w1++;

        /* Do the last few bytes of comparison a byte at a time.  */
        p0 = (char *) w0;
        p1 = (char *) w1;
        while (*p0 == *p1)
            p0++, p1++;

        /* Don't mistakenly count missing newline as part of
           prefix.  */
        if (false
            && ((buffer0 + n0 - filevec[0].missing_newline < p0)
                !=
                (buffer1 + n1 - filevec[1].missing_newline < p1)))
            p0--, p1--;
    }

    /* Now |p0| and |p1| point at the first nonmatching
       characters.  */

    /* Skip back to last line-beginning in the prefix, and then
       discard up to |horizon_lines| lines from the prefix.  */
    i = horizon_lines;
    while (p0 != buffer0 && (p0[-1] != '\n' || i--))
        p0--, p1--;

    /* Record the prefix.  */
    filevec[0].prefix_end = p0;
    filevec[1].prefix_end = p1;

    /* Find identical suffix.  */

    /* |p0| and |p1| point beyond the last chars not yet compared.  */
    p0 = buffer0 + n0;
    p1 = buffer1 + n1;

    if (filevec[0].missing_newline == filevec[1].missing_newline) {
        end0 = p0;    /* Addr of last char in file 0.  */

        /* Get value of |p0| at which we should stop scanning
       backward: this is when either |p0| or |p1| points just past the
       last char of the identical prefix.  */
        beg0 = filevec[0].prefix_end + (n0 < n1 ? 0 : n0 - n1);

        /* Scan back until chars don't match or we reach that point.  */
        while (p0 != beg0)
            if (*--p0 != *--p1) {
                /* Point at the first char of the matching suffix.  */
                ++p0, ++p1;
                beg0 = p0;
                break;
            }

        /* Are we at a line-beginning in both files?  If not, add the
       rest of this line to the main body.  Discard up to
       |horizon_lines| lines from the identical suffix.  Also, discard
       one extra line, because |shift_boundaries| may need it.  */
        i = horizon_lines + !((buffer0 == p0 || p0[-1] == '\n')
                              &&
                              (buffer1 == p1 || p1[-1] == '\n'));
        while (i-- && p0 != end0)
            while (*p0++ != '\n')
                continue;

        p1 += p0 - beg0;
    }

    /* Record the suffix.  */
    filevec[0].suffix_begin = p0;
    filevec[1].suffix_begin = p1;

    /* Calculate number of lines of prefix to save.

       |prefix_count == 0| means save the whole prefix; we need this
       for options like |-D| that output the whole file, or for
       enormous contexts (to avoid worrying about arithmetic
       overflow).  We also need it for options like |-F| that output
       some preceding line; at least we will need to find the last few
       lines, but since we don't know how many, it's easiest to find
       them all.

       Otherwise, |prefix_count != 0|.  Save just |prefix_count| lines
       at start of the line buffer; they'll be moved to the proper
       location later.  Handle 1 more line than the context says
       (because we count 1 too many), rounded up to the next power of
       2 to speed index computation.  */

    prefix_count = 0;
    alloc_lines0 = guess_lines(0, 0, n0);
    prefix_mask = prefix_count - 1;
    lines = 0;
    linbuf0 = xmalloc(alloc_lines0 * sizeof *linbuf0);
    p0 = buffer0;

    /* If the prefix is needed, find the prefix lines.  */
    end0 = filevec[0].prefix_end;
    while (p0 != end0) {
        lin l = lines++ & prefix_mask;
        if (l == alloc_lines0) {
            if (PTRDIFF_MAX / (2 * sizeof *linbuf0) <= alloc_lines0)
                xalloc_die();
            alloc_lines0 *= 2;
            linbuf0 = xrealloc(linbuf0, alloc_lines0 * sizeof *linbuf0);
        }
        linbuf0[l] = p0;
        while (*p0++ != '\n')
            continue;
    }
    buffered_prefix = prefix_count && context < lines ? context : lines;

    /* Allocate line buffer 1.  */

    middle_guess = guess_lines(lines, p0 - buffer0, p1 - filevec[1].prefix_end);
    suffix_guess = guess_lines(lines, p0 - buffer0, buffer1 + n1 - p1);
    alloc_lines1 = buffered_prefix + middle_guess + MIN (context, suffix_guess);
    if (alloc_lines1 < buffered_prefix
        || PTRDIFF_MAX / sizeof *linbuf1 <= alloc_lines1)
        xalloc_die();
    linbuf1 = xmalloc(alloc_lines1 * sizeof *linbuf1);

    if (buffered_prefix != lines) {
        /* Rotate prefix lines to proper location.  */
        for (i = 0; i < buffered_prefix; i++)
            linbuf1[i] = linbuf0[(lines - context + i) & prefix_mask];
        for (i = 0; i < buffered_prefix; i++)
            linbuf0[i] = linbuf1[i];
    }

    /* Initialize line buffer 1 from line buffer 0.  */
    for (i = 0; i < buffered_prefix; i++)
        linbuf1[i] = linbuf0[i] - buffer0 + buffer1;

    /* Record the line buffer, adjusted so that
       |linbuf[0]| points at the first differing line.  */
    filevec[0].linbuf = linbuf0 + buffered_prefix;
    filevec[1].linbuf = linbuf1 + buffered_prefix;
    filevec[0].linbuf_base = filevec[1].linbuf_base = -buffered_prefix;
    filevec[0].alloc_lines = alloc_lines0 - buffered_prefix;
    filevec[1].alloc_lines = alloc_lines1 - buffered_prefix;
    filevec[0].prefix_lines = filevec[1].prefix_lines = lines;
}

/* If $1 < k$, then $(2^k - {\rm prime\_offset}_k)$ is the largest
   prime less than $2^k$.  This table is derived from
   Chris~K.~Caldwell's list
   \url{http://www.utm.edu/research/primes/lists/2small/}.  */

static unsigned char const prime_offset[] =
        {
                0, 0, 1, 1, 3, 1, 3, 1, 5, 3, 3, 9, 3, 1, 3, 19, 15, 1, 5, 1, 3, 9, 3,
                15, 3, 39, 5, 39, 57, 3, 35, 1, 5, 9, 41, 31, 5, 25, 45, 7, 87, 21,
                11, 57, 17, 55, 21, 115, 59, 81, 27, 129, 47, 111, 33, 55, 5, 13, 27,
                55, 93, 1, 57, 25
        };

/* Given a vector of two |file_data| objects, read the file associated
   with each one, and build the table of equivalence classes.  Return
   nonzero if either file appears to be a binary file.  If
   |pretend_binary| is nonzero, pretend they are binary
   regardless.  */

bool
read_files(struct file_data filevec[], bool pretend_binary) {
    int i;
    bool skip_test = text | pretend_binary;
    bool appears_binary = pretend_binary | sip(&filevec[0], skip_test);

    if (filevec[0].desc != filevec[1].desc)
        appears_binary |= sip(&filevec[1], skip_test | appears_binary);
    else {
        filevec[1].buffer = filevec[0].buffer;
        filevec[1].bufsize = filevec[0].bufsize;
        filevec[1].buffered = filevec[0].buffered;
    }
    if (appears_binary) {
        return true;
    }

    find_identical_ends(filevec);

    equivs_alloc = filevec[0].alloc_lines + filevec[1].alloc_lines + 1;
    if (PTRDIFF_MAX / sizeof *equivs <= equivs_alloc)
        xalloc_die();
    equivs = xmalloc(equivs_alloc * sizeof *equivs);
    /* Equivalence class 0 is permanently safe for lines that were not
       hashed.  Real equivalence classes start at 1.  */
    equivs_index = 1;

    /* Allocate (one plus) a prime number of hash buckets.  Use a
       prime number between $1/3$ and $2/3$ of the value of
       |equiv_allocs|, approximately.  */
    for (i = 9; (size_t) 1 << i < equivs_alloc / 3; i++)
        continue;
    nbuckets = ((size_t) 1 << i) - prime_offset[i];
    if (PTRDIFF_MAX / sizeof *buckets <= nbuckets)
        xalloc_die();
    buckets = zalloc((nbuckets + 1) * sizeof *buckets);
    buckets++;

    for (i = 0; i < 2; i++)
        find_and_hash_each_line(&filevec[i]);

    filevec[0].equiv_max = filevec[1].equiv_max = equivs_index;

    free(equivs);
    free(buckets - 1);

    return false;
}