utf8: teach same_encoding() alternative UTF encoding names

[alt-git.git] / utf8.c

#include "git-compat-util.h"
#include "strbuf.h"
#include "utf8.h"

/* This code is originally from http://www.cl.cam.ac.uk/~mgk25/ucs/ */

struct interval {
        ucs_char_t first;
        ucs_char_t last;
};

size_t display_mode_esc_sequence_len(const char *s)
{
        const char *p = s;
        if (*p++ != '\033')
                return 0;
        if (*p++ != '[')
                return 0;
        while (isdigit(*p) || *p == ';')
                p++;
        if (*p++ != 'm')
                return 0;
        return p - s;
}

/* auxiliary function for binary search in interval table */
static int bisearch(ucs_char_t ucs, const struct interval *table, int max)
{
        int min = 0;
        int mid;

        if (ucs < table[0].first || ucs > table[max].last)
                return 0;
        while (max >= min) {
                mid = min + (max - min) / 2;
                if (ucs > table[mid].last)
                        min = mid + 1;
                else if (ucs < table[mid].first)
                        max = mid - 1;
                else
                        return 1;
        }

        return 0;
}

/* The following two functions define the column width of an ISO 10646
 * character as follows:
 *
 *    - The null character (U+0000) has a column width of 0.
 *
 *    - Other C0/C1 control characters and DEL will lead to a return
 *      value of -1.
 *
 *    - Non-spacing and enclosing combining characters (general
 *      category code Mn or Me in the Unicode database) have a
 *      column width of 0.
 *
 *    - SOFT HYPHEN (U+00AD) has a column width of 1.
 *
 *    - Other format characters (general category code Cf in the Unicode
 *      database) and ZERO WIDTH SPACE (U+200B) have a column width of 0.
 *
 *    - Hangul Jamo medial vowels and final consonants (U+1160-U+11FF)
 *      have a column width of 0.
 *
 *    - Spacing characters in the East Asian Wide (W) or East Asian
 *      Full-width (F) category as defined in Unicode Technical
 *      Report #11 have a column width of 2.
 *
 *    - All remaining characters (including all printable
 *      ISO 8859-1 and WGL4 characters, Unicode control characters,
 *      etc.) have a column width of 1.
 *
 * This implementation assumes that ucs_char_t characters are encoded
 * in ISO 10646.
 */

static int git_wcwidth(ucs_char_t ch)
{
        /*
         * Sorted list of non-overlapping intervals of non-spacing characters,
         */
#include "unicode_width.h"

        /* test for 8-bit control characters */
        if (ch == 0)
                return 0;
        if (ch < 32 || (ch >= 0x7f && ch < 0xa0))
                return -1;

        /* binary search in table of non-spacing characters */
        if (bisearch(ch, zero_width, sizeof(zero_width)
                                / sizeof(struct interval) - 1))
                return 0;

        /* binary search in table of double width characters */
        if (bisearch(ch, double_width, sizeof(double_width)
                                / sizeof(struct interval) - 1))
                return 2;

        return 1;
}

/*
 * Pick one ucs character starting from the location *start points at,
 * and return it, while updating the *start pointer to point at the
 * end of that character.  When remainder_p is not NULL, the location
 * holds the number of bytes remaining in the string that we are allowed
 * to pick from.  Otherwise we are allowed to pick up to the NUL that
 * would eventually appear in the string.  *remainder_p is also reduced
 * by the number of bytes we have consumed.
 *
 * If the string was not a valid UTF-8, *start pointer is set to NULL
 * and the return value is undefined.
 */
static ucs_char_t pick_one_utf8_char(const char **start, size_t *remainder_p)
{
        unsigned char *s = (unsigned char *)*start;
        ucs_char_t ch;
        size_t remainder, incr;

        /*
         * A caller that assumes NUL terminated text can choose
         * not to bother with the remainder length.  We will
         * stop at the first NUL.
         */
        remainder = (remainder_p ? *remainder_p : 999);

        if (remainder < 1) {
                goto invalid;
        } else if (*s < 0x80) {
                /* 0xxxxxxx */
                ch = *s;
                incr = 1;
        } else if ((s[0] & 0xe0) == 0xc0) {
                /* 110XXXXx 10xxxxxx */
                if (remainder < 2 ||
                    (s[1] & 0xc0) != 0x80 ||
                    (s[0] & 0xfe) == 0xc0)
                        goto invalid;
                ch = ((s[0] & 0x1f) << 6) | (s[1] & 0x3f);
                incr = 2;
        } else if ((s[0] & 0xf0) == 0xe0) {
                /* 1110XXXX 10Xxxxxx 10xxxxxx */
                if (remainder < 3 ||
                    (s[1] & 0xc0) != 0x80 ||
                    (s[2] & 0xc0) != 0x80 ||
                    /* overlong? */
                    (s[0] == 0xe0 && (s[1] & 0xe0) == 0x80) ||
                    /* surrogate? */
                    (s[0] == 0xed && (s[1] & 0xe0) == 0xa0) ||
                    /* U+FFFE or U+FFFF? */
                    (s[0] == 0xef && s[1] == 0xbf &&
                     (s[2] & 0xfe) == 0xbe))
                        goto invalid;
                ch = ((s[0] & 0x0f) << 12) |
                        ((s[1] & 0x3f) << 6) | (s[2] & 0x3f);
                incr = 3;
        } else if ((s[0] & 0xf8) == 0xf0) {
                /* 11110XXX 10XXxxxx 10xxxxxx 10xxxxxx */
                if (remainder < 4 ||
                    (s[1] & 0xc0) != 0x80 ||
                    (s[2] & 0xc0) != 0x80 ||
                    (s[3] & 0xc0) != 0x80 ||
                    /* overlong? */
                    (s[0] == 0xf0 && (s[1] & 0xf0) == 0x80) ||
                    /* > U+10FFFF? */
                    (s[0] == 0xf4 && s[1] > 0x8f) || s[0] > 0xf4)
                        goto invalid;
                ch = ((s[0] & 0x07) << 18) | ((s[1] & 0x3f) << 12) |
                        ((s[2] & 0x3f) << 6) | (s[3] & 0x3f);
                incr = 4;
        } else {
invalid:
                *start = NULL;
                return 0;
        }

        *start += incr;
        if (remainder_p)
                *remainder_p = remainder - incr;
        return ch;
}

/*
 * This function returns the number of columns occupied by the character
 * pointed to by the variable start. The pointer is updated to point at
 * the next character. When remainder_p is not NULL, it points at the
 * location that stores the number of remaining bytes we can use to pick
 * a character (see pick_one_utf8_char() above).
 */
int utf8_width(const char **start, size_t *remainder_p)
{
        ucs_char_t ch = pick_one_utf8_char(start, remainder_p);
        if (!*start)
                return 0;
        return git_wcwidth(ch);
}

/*
 * Returns the total number of columns required by a null-terminated
 * string, assuming that the string is utf8.  Returns strlen() instead
 * if the string does not look like a valid utf8 string.
 */
int utf8_strnwidth(const char *string, int len, int skip_ansi)
{
        int width = 0;
        const char *orig = string;

        if (len == -1)
                len = strlen(string);
        while (string && string < orig + len) {
                int skip;
                while (skip_ansi &&
                       (skip = display_mode_esc_sequence_len(string)) != 0)
                        string += skip;
                width += utf8_width(&string, NULL);
        }
        return string ? width : len;
}

int utf8_strwidth(const char *string)
{
        return utf8_strnwidth(string, -1, 0);
}

int is_utf8(const char *text)
{
        while (*text) {
                if (*text == '\n' || *text == '\t' || *text == '\r') {
                        text++;
                        continue;
                }
                utf8_width(&text, NULL);
                if (!text)
                        return 0;
        }
        return 1;
}

static void strbuf_add_indented_text(struct strbuf *buf, const char *text,
                                     int indent, int indent2)
{
        if (indent < 0)
                indent = 0;
        while (*text) {
                const char *eol = strchrnul(text, '\n');
                if (*eol == '\n')
                        eol++;
                strbuf_addchars(buf, ' ', indent);
                strbuf_add(buf, text, eol - text);
                text = eol;
                indent = indent2;
        }
}

/*
 * Wrap the text, if necessary. The variable indent is the indent for the
 * first line, indent2 is the indent for all other lines.
 * If indent is negative, assume that already -indent columns have been
 * consumed (and no extra indent is necessary for the first line).
 */
void strbuf_add_wrapped_text(struct strbuf *buf,
                const char *text, int indent1, int indent2, int width)
{
        int indent, w, assume_utf8 = 1;
        const char *bol, *space, *start = text;
        size_t orig_len = buf->len;

        if (width <= 0) {
                strbuf_add_indented_text(buf, text, indent1, indent2);
                return;
        }

retry:
        bol = text;
        w = indent = indent1;
        space = NULL;
        if (indent < 0) {
                w = -indent;
                space = text;
        }

        for (;;) {
                char c;
                size_t skip;

                while ((skip = display_mode_esc_sequence_len(text)))
                        text += skip;

                c = *text;
                if (!c || isspace(c)) {
                        if (w <= width || !space) {
                                const char *start = bol;
                                if (!c && text == start)
                                        return;
                                if (space)
                                        start = space;
                                else
                                        strbuf_addchars(buf, ' ', indent);
                                strbuf_add(buf, start, text - start);
                                if (!c)
                                        return;
                                space = text;
                                if (c == '\t')
                                        w |= 0x07;
                                else if (c == '\n') {
                                        space++;
                                        if (*space == '\n') {
                                                strbuf_addch(buf, '\n');
                                                goto new_line;
                                        }
                                        else if (!isalnum(*space))
                                                goto new_line;
                                        else
                                                strbuf_addch(buf, ' ');
                                }
                                w++;
                                text++;
                        }
                        else {
new_line:
                                strbuf_addch(buf, '\n');
                                text = bol = space + isspace(*space);
                                space = NULL;
                                w = indent = indent2;
                        }
                        continue;
                }
                if (assume_utf8) {
                        w += utf8_width(&text, NULL);
                        if (!text) {
                                assume_utf8 = 0;
                                text = start;
                                strbuf_setlen(buf, orig_len);
                                goto retry;
                        }
                } else {
                        w++;
                        text++;
                }
        }
}

void strbuf_add_wrapped_bytes(struct strbuf *buf, const char *data, int len,
                             int indent, int indent2, int width)
{
        char *tmp = xstrndup(data, len);
        strbuf_add_wrapped_text(buf, tmp, indent, indent2, width);
        free(tmp);
}

void strbuf_utf8_replace(struct strbuf *sb_src, int pos, int width,
                         const char *subst)
{
        struct strbuf sb_dst = STRBUF_INIT;
        char *src = sb_src->buf;
        char *end = src + sb_src->len;
        char *dst;
        int w = 0, subst_len = 0;

        if (subst)
                subst_len = strlen(subst);
        strbuf_grow(&sb_dst, sb_src->len + subst_len);
        dst = sb_dst.buf;

        while (src < end) {
                char *old;
                size_t n;

                while ((n = display_mode_esc_sequence_len(src))) {
                        memcpy(dst, src, n);
                        src += n;
                        dst += n;
                }

                if (src >= end)
                        break;

                old = src;
                n = utf8_width((const char**)&src, NULL);
                if (!src)       /* broken utf-8, do nothing */
                        goto out;
                if (n && w >= pos && w < pos + width) {
                        if (subst) {
                                memcpy(dst, subst, subst_len);
                                dst += subst_len;
                                subst = NULL;
                        }
                        w += n;
                        continue;
                }
                memcpy(dst, old, src - old);
                dst += src - old;
                w += n;
        }
        strbuf_setlen(&sb_dst, dst - sb_dst.buf);
        strbuf_swap(sb_src, &sb_dst);
out:
        strbuf_release(&sb_dst);
}

/*
 * Returns true (1) if the src encoding name matches the dst encoding
 * name directly or one of its alternative names. E.g. UTF-16BE is the
 * same as UTF16BE.
 */
static int same_utf_encoding(const char *src, const char *dst)
{
        if (istarts_with(src, "utf") && istarts_with(dst, "utf")) {
                /* src[3] or dst[3] might be '\0' */
                int i = (src[3] == '-' ? 4 : 3);
                int j = (dst[3] == '-' ? 4 : 3);
                return !strcasecmp(src+i, dst+j);
        }
        return 0;
}

int is_encoding_utf8(const char *name)
{
        if (!name)
                return 1;
        if (same_utf_encoding("utf-8", name))
                return 1;
        return 0;
}

int same_encoding(const char *src, const char *dst)
{
        static const char utf8[] = "UTF-8";

        if (!src)
                src = utf8;
        if (!dst)
                dst = utf8;
        if (same_utf_encoding(src, dst))
                return 1;
        return !strcasecmp(src, dst);
}

/*
 * Wrapper for fprintf and returns the total number of columns required
 * for the printed string, assuming that the string is utf8.
 */
int utf8_fprintf(FILE *stream, const char *format, ...)
{
        struct strbuf buf = STRBUF_INIT;
        va_list arg;
        int columns;

        va_start(arg, format);
        strbuf_vaddf(&buf, format, arg);
        va_end(arg);

        columns = fputs(buf.buf, stream);
        if (0 <= columns) /* keep the error from the I/O */
                columns = utf8_strwidth(buf.buf);
        strbuf_release(&buf);
        return columns;
}

/*
 * Given a buffer and its encoding, return it re-encoded
 * with iconv.  If the conversion fails, returns NULL.
 */
#ifndef NO_ICONV
#if defined(OLD_ICONV) || (defined(__sun__) && !defined(_XPG6))
        typedef const char * iconv_ibp;
#else
        typedef char * iconv_ibp;
#endif
char *reencode_string_iconv(const char *in, size_t insz, iconv_t conv, int *outsz_p)
{
        size_t outsz, outalloc;
        char *out, *outpos;
        iconv_ibp cp;

        outsz = insz;
        outalloc = outsz + 1; /* for terminating NUL */
        out = xmalloc(outalloc);
        outpos = out;
        cp = (iconv_ibp)in;

        while (1) {
                size_t cnt = iconv(conv, &cp, &insz, &outpos, &outsz);

                if (cnt == (size_t) -1) {
                        size_t sofar;
                        if (errno != E2BIG) {
                                free(out);
                                return NULL;
                        }
                        /* insz has remaining number of bytes.
                         * since we started outsz the same as insz,
                         * it is likely that insz is not enough for
                         * converting the rest.
                         */
                        sofar = outpos - out;
                        outalloc = sofar + insz * 2 + 32;
                        out = xrealloc(out, outalloc);
                        outpos = out + sofar;
                        outsz = outalloc - sofar - 1;
                }
                else {
                        *outpos = '\0';
                        if (outsz_p)
                                *outsz_p = outpos - out;
                        break;
                }
        }
        return out;
}

static const char *fallback_encoding(const char *name)
{
        /*
         * Some platforms do not have the variously spelled variants of
         * UTF-8, so let's fall back to trying the most official
         * spelling. We do so only as a fallback in case the platform
         * does understand the user's spelling, but not our official
         * one.
         */
        if (is_encoding_utf8(name))
                return "UTF-8";

        /*
         * Even though latin-1 is still seen in e-mail
         * headers, some platforms only install ISO-8859-1.
         */
        if (!strcasecmp(name, "latin-1"))
                return "ISO-8859-1";

        return name;
}

char *reencode_string_len(const char *in, int insz,
                          const char *out_encoding, const char *in_encoding,
                          int *outsz)
{
        iconv_t conv;
        char *out;

        if (!in_encoding)
                return NULL;

        conv = iconv_open(out_encoding, in_encoding);
        if (conv == (iconv_t) -1) {
                in_encoding = fallback_encoding(in_encoding);
                out_encoding = fallback_encoding(out_encoding);

                conv = iconv_open(out_encoding, in_encoding);
                if (conv == (iconv_t) -1)
                        return NULL;
        }

        out = reencode_string_iconv(in, insz, conv, outsz);
        iconv_close(conv);
        return out;
}
#endif

/*
 * Returns first character length in bytes for multi-byte `text` according to
 * `encoding`.
 *
 * - The `text` pointer is updated to point at the next character.
 * - When `remainder_p` is not NULL, on entry `*remainder_p` is how much bytes
 *   we can consume from text, and on exit `*remainder_p` is reduced by returned
 *   character length. Otherwise `text` is treated as limited by NUL.
 */
int mbs_chrlen(const char **text, size_t *remainder_p, const char *encoding)
{
        int chrlen;
        const char *p = *text;
        size_t r = (remainder_p ? *remainder_p : SIZE_MAX);

        if (r < 1)
                return 0;

        if (is_encoding_utf8(encoding)) {
                pick_one_utf8_char(&p, &r);

                chrlen = p ? (p - *text)
                           : 1 /* not valid UTF-8 -> raw byte sequence */;
        }
        else {
                /*
                 * TODO use iconv to decode one char and obtain its chrlen
                 * for now, let's treat encodings != UTF-8 as one-byte
                 */
                chrlen = 1;
        }

        *text += chrlen;
        if (remainder_p)
                *remainder_p -= chrlen;

        return chrlen;
}

/*
 * Pick the next char from the stream, ignoring codepoints an HFS+ would.
 * Note that this is _not_ complete by any means. It's just enough
 * to make is_hfs_dotgit() work, and should not be used otherwise.
 */
static ucs_char_t next_hfs_char(const char **in)
{
        while (1) {
                ucs_char_t out = pick_one_utf8_char(in, NULL);
                /*
                 * check for malformed utf8. Technically this
                 * gets converted to a percent-sequence, but
                 * returning 0 is good enough for is_hfs_dotgit
                 * to realize it cannot be .git
                 */
                if (!*in)
                        return 0;

                /* these code points are ignored completely */
                switch (out) {
                case 0x200c: /* ZERO WIDTH NON-JOINER */
                case 0x200d: /* ZERO WIDTH JOINER */
                case 0x200e: /* LEFT-TO-RIGHT MARK */
                case 0x200f: /* RIGHT-TO-LEFT MARK */
                case 0x202a: /* LEFT-TO-RIGHT EMBEDDING */
                case 0x202b: /* RIGHT-TO-LEFT EMBEDDING */
                case 0x202c: /* POP DIRECTIONAL FORMATTING */
                case 0x202d: /* LEFT-TO-RIGHT OVERRIDE */
                case 0x202e: /* RIGHT-TO-LEFT OVERRIDE */
                case 0x206a: /* INHIBIT SYMMETRIC SWAPPING */
                case 0x206b: /* ACTIVATE SYMMETRIC SWAPPING */
                case 0x206c: /* INHIBIT ARABIC FORM SHAPING */
                case 0x206d: /* ACTIVATE ARABIC FORM SHAPING */
                case 0x206e: /* NATIONAL DIGIT SHAPES */
                case 0x206f: /* NOMINAL DIGIT SHAPES */
                case 0xfeff: /* ZERO WIDTH NO-BREAK SPACE */
                        continue;
                }

                return out;
        }
}

int is_hfs_dotgit(const char *path)
{
        ucs_char_t c;

        c = next_hfs_char(&path);
        if (c != '.')
                return 0;
        c = next_hfs_char(&path);

        /*
         * there's a great deal of other case-folding that occurs
         * in HFS+, but this is enough to catch anything that will
         * convert to ".git"
         */
        if (c != 'g' && c != 'G')
                return 0;
        c = next_hfs_char(&path);
        if (c != 'i' && c != 'I')
                return 0;
        c = next_hfs_char(&path);
        if (c != 't' && c != 'T')
                return 0;
        c = next_hfs_char(&path);
        if (c && !is_dir_sep(c))
                return 0;

        return 1;
}

const char utf8_bom[] = "\357\273\277";

int skip_utf8_bom(char **text, size_t len)
{
        if (len < strlen(utf8_bom) ||
            memcmp(*text, utf8_bom, strlen(utf8_bom)))
                return 0;
        *text += strlen(utf8_bom);
        return 1;
}

void strbuf_utf8_align(struct strbuf *buf, align_type position, unsigned int width,
                       const char *s)
{
        int slen = strlen(s);
        int display_len = utf8_strnwidth(s, slen, 0);
        int utf8_compensation = slen - display_len;

        if (display_len >= width) {
                strbuf_addstr(buf, s);
                return;
        }

        if (position == ALIGN_LEFT)
                strbuf_addf(buf, "%-*s", width + utf8_compensation, s);
        else if (position == ALIGN_MIDDLE) {
                int left = (width - display_len) / 2;
                strbuf_addf(buf, "%*s%-*s", left, "", width - left + utf8_compensation, s);
        } else if (position == ALIGN_RIGHT)
                strbuf_addf(buf, "%*s", width + utf8_compensation, s);
}