re2/util/rune.cc

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/*
 * The authors of this software are Rob Pike and Ken Thompson.
 *              Copyright (c) 2002 by Lucent Technologies.
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */
 
#include <stdarg.h>
#include <string.h>
 
#include "util/utf.h"
 
namespace re2 {
 
enum
{
        Bit1    = 7,
        Bitx    = 6,
        Bit2    = 5,
        Bit3    = 4,
        Bit4    = 3,
        Bit5    = 2, 
 
        T1      = ((1<<(Bit1+1))-1) ^ 0xFF,     /* 0000 0000 */
        Tx      = ((1<<(Bitx+1))-1) ^ 0xFF,     /* 1000 0000 */
        T2      = ((1<<(Bit2+1))-1) ^ 0xFF,     /* 1100 0000 */
        T3      = ((1<<(Bit3+1))-1) ^ 0xFF,     /* 1110 0000 */
        T4      = ((1<<(Bit4+1))-1) ^ 0xFF,     /* 1111 0000 */
        T5      = ((1<<(Bit5+1))-1) ^ 0xFF,     /* 1111 1000 */
 
        Rune1   = (1<<(Bit1+0*Bitx))-1,         /* 0000 0000 0111 1111 */
        Rune2   = (1<<(Bit2+1*Bitx))-1,         /* 0000 0111 1111 1111 */
        Rune3   = (1<<(Bit3+2*Bitx))-1,         /* 1111 1111 1111 1111 */
        Rune4   = (1<<(Bit4+3*Bitx))-1,
                                        /* 0001 1111 1111 1111 1111 1111 */
 
        Maskx   = (1<<Bitx)-1,                  /* 0011 1111 */
        Testx   = Maskx ^ 0xFF,                 /* 1100 0000 */
 
        Bad     = Runeerror,
};
 
int
chartorune(Rune *rune, const char *str)
{
        int c, c1, c2, c3;
        long l;
 
        /*
         * one character sequence
         *      00000-0007F => T1
         */
        c = *(unsigned char*)str;
        if(c < Tx) {
                *rune = c;
                return 1;
        }
 
        /*
         * two character sequence
         *      0080-07FF => T2 Tx
         */
        c1 = *(unsigned char*)(str+1) ^ Tx;
        if(c1 & Testx)
                goto bad;
        if(c < T3) {
                if(c < T2)
                        goto bad;
                l = ((c << Bitx) | c1) & Rune2;
                if(l <= Rune1)
                        goto bad;
                *rune = l;
                return 2;
        }
 
        /*
         * three character sequence
         *      0800-FFFF => T3 Tx Tx
         */
        c2 = *(unsigned char*)(str+2) ^ Tx;
        if(c2 & Testx)
                goto bad;
        if(c < T4) {
                l = ((((c << Bitx) | c1) << Bitx) | c2) & Rune3;
                if(l <= Rune2)
                        goto bad;
                *rune = l;
                return 3;
        }
 
        /*
         * four character sequence (21-bit value)
         *      10000-1FFFFF => T4 Tx Tx Tx
         */
        c3 = *(unsigned char*)(str+3) ^ Tx;
        if (c3 & Testx)
                goto bad;
        if (c < T5) {
                l = ((((((c << Bitx) | c1) << Bitx) | c2) << Bitx) | c3) & Rune4;
                if (l <= Rune3)
                        goto bad;
                *rune = l;
                return 4;
        }
 
        /*
         * Support for 5-byte or longer UTF-8 would go here, but
         * since we don't have that, we'll just fall through to bad.
         */
 
        /*
         * bad decoding
         */
bad:
        *rune = Bad;
        return 1;
}
 
int
runetochar(char *str, const Rune *rune)
{
        /* Runes are signed, so convert to unsigned for range check. */
        unsigned long c;
 
        /*
         * one character sequence
         *      00000-0007F => 00-7F
         */
        c = *rune;
        if(c <= Rune1) {
                str[0] = static_cast<char>(c);
                return 1;
        }
 
        /*
         * two character sequence
         *      0080-07FF => T2 Tx
         */
        if(c <= Rune2) {
                str[0] = T2 | static_cast<char>(c >> 1*Bitx);
                str[1] = Tx | (c & Maskx);
                return 2;
        }
 
        /*
         * If the Rune is out of range, convert it to the error rune.
         * Do this test here because the error rune encodes to three bytes.
         * Doing it earlier would duplicate work, since an out of range
         * Rune wouldn't have fit in one or two bytes.
         */
        if (c > Runemax)
                c = Runeerror;
 
        /*
         * three character sequence
         *      0800-FFFF => T3 Tx Tx
         */
        if (c <= Rune3) {
                str[0] = T3 | static_cast<char>(c >> 2*Bitx);
                str[1] = Tx | ((c >> 1*Bitx) & Maskx);
                str[2] = Tx | (c & Maskx);
                return 3;
        }
 
        /*
         * four character sequence (21-bit value)
         *     10000-1FFFFF => T4 Tx Tx Tx
         */
        str[0] = T4 | static_cast<char>(c >> 3*Bitx);
        str[1] = Tx | ((c >> 2*Bitx) & Maskx);
        str[2] = Tx | ((c >> 1*Bitx) & Maskx);
        str[3] = Tx | (c & Maskx);
        return 4;
}
 
int
runelen(Rune rune)
{
        char str[10];
 
        return runetochar(str, &rune);
}
 
int
fullrune(const char *str, int n)
{
        if (n > 0) {
                int c = *(unsigned char*)str;
                if (c < Tx)
                        return 1;
                if (n > 1) {
                        if (c < T3)
                                return 1;
                        if (n > 2) {
                                if (c < T4 || n > 3)
                                        return 1;
                        }
                }
        }
        return 0;
}
 
 
int
utflen(const char *s)
{
        int c;
        long n;
        Rune rune;
 
        n = 0;
        for(;;) {
                c = *(unsigned char*)s;
                if(c < Runeself) {
                        if(c == 0)
                                return n;
                        s++;
                } else
                        s += chartorune(&rune, s);
                n++;
        }
        return 0;
}
 
char*
utfrune(const char *s, Rune c)
{
        long c1;
        Rune r;
        int n;
 
        if(c < Runesync)                /* not part of utf sequence */
                return strchr((char*)s, c);
 
        for(;;) {
                c1 = *(unsigned char*)s;
                if(c1 < Runeself) {     /* one byte rune */
                        if(c1 == 0)
                                return 0;
                        if(c1 == c)
                                return (char*)s;
                        s++;
                        continue;
                }
                n = chartorune(&r, s);
                if(r == c)
                        return (char*)s;
                s += n;
        }
        return 0;
}
 
}  // namespace re2