comparison src/Support/ConvertUTF.c @ 0:582cbe817f2c

- Initial add of support code and modules. Not everything is working yet.

+/*
+ * Copyright 2001-2004 Unicode, Inc.
+ * 
+ * Disclaimer
+ * 
+ * This source code is provided as is by Unicode, Inc. No claims are
+ * made as to fitness for any particular purpose. No warranties of any
+ * kind are expressed or implied. The recipient agrees to determine
+ * applicability of information provided. If this file has been
+ * purchased on magnetic or optical media from Unicode, Inc., the
+ * sole remedy for any claim will be exchange of defective media
+ * within 90 days of receipt.
+ * 
+ * Limitations on Rights to Redistribute This Code
+ * 
+ * Unicode, Inc. hereby grants the right to freely use the information
+ * supplied in this file in the creation of products supporting the
+ * Unicode Standard, and to make copies of this file in any form
+ * for internal or external distribution as long as this notice
+ * remains attached.
+ */
+
+/* ---------------------------------------------------------------------
+
+    Conversions between UTF32, UTF-16, and UTF-8. Source code file.
+    Author: Mark E. Davis, 1994.
+    Rev History: Rick McGowan, fixes & updates May 2001.
+    Sept 2001: fixed const & error conditions per
+	mods suggested by S. Parent & A. Lillich.
+    June 2002: Tim Dodd added detection and handling of incomplete
+	source sequences, enhanced error detection, added casts
+	to eliminate compiler warnings.
+    July 2003: slight mods to back out aggressive FFFE detection.
+    Jan 2004: updated switches in from-UTF8 conversions.
+    Oct 2004: updated to use UNI_MAX_LEGAL_UTF32 in UTF-32 conversions.
+
+    See the header file "ConvertUTF.h" for complete documentation.
+
+------------------------------------------------------------------------ */
+
+
+#include "ConvertUTF.h"
+#ifdef CVTUTF_DEBUG
+#include <stdio.h>
+#endif
+
+static const int halfShift  = 10; /* used for shifting by 10 bits */
+
+static const UTF32 halfBase = 0x0010000UL;
+static const UTF32 halfMask = 0x3FFUL;
+
+#define UNI_SUR_HIGH_START  (UTF32)0xD800
+#define UNI_SUR_HIGH_END    (UTF32)0xDBFF
+#define UNI_SUR_LOW_START   (UTF32)0xDC00
+#define UNI_SUR_LOW_END     (UTF32)0xDFFF
+#define false	   0
+#define true	    1
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF32toUTF16 (
+	const UTF32** sourceStart, const UTF32* sourceEnd, 
+	UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF32* source = *sourceStart;
+    UTF16* target = *targetStart;
+    while (source < sourceEnd) {
+	UTF32 ch;
+	if (target >= targetEnd) {
+	    result = targetExhausted; break;
+	}
+	ch = *source++;
+	if (ch <= UNI_MAX_BMP) { /* Target is a character <= 0xFFFF */
+	    /* UTF-16 surrogate values are illegal in UTF-32; 0xffff or 0xfffe are both reserved values */
+	    if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) {
+		if (flags == strictConversion) {
+		    --source; /* return to the illegal value itself */
+		    result = sourceIllegal;
+		    break;
+		} else {
+		    *target++ = UNI_REPLACEMENT_CHAR;
+		}
+	    } else {
+		*target++ = (UTF16)ch; /* normal case */
+	    }
+	} else if (ch > UNI_MAX_LEGAL_UTF32) {
+	    if (flags == strictConversion) {
+		result = sourceIllegal;
+	    } else {
+		*target++ = UNI_REPLACEMENT_CHAR;
+	    }
+	} else {
+	    /* target is a character in range 0xFFFF - 0x10FFFF. */
+	    if (target + 1 >= targetEnd) {
+		--source; /* Back up source pointer! */
+		result = targetExhausted; break;
+	    }
+	    ch -= halfBase;
+	    *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);
+	    *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);
+	}
+    }
+    *sourceStart = source;
+    *targetStart = target;
+    return result;
+}
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF16toUTF32 (
+	const UTF16** sourceStart, const UTF16* sourceEnd, 
+	UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF16* source = *sourceStart;
+    UTF32* target = *targetStart;
+    UTF32 ch, ch2;
+    while (source < sourceEnd) {
+	const UTF16* oldSource = source; /*  In case we have to back up because of target overflow. */
+	ch = *source++;
+	/* If we have a surrogate pair, convert to UTF32 first. */
+	if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) {
+	    /* If the 16 bits following the high surrogate are in the source buffer... */
+	    if (source < sourceEnd) {
+		ch2 = *source;
+		/* If it's a low surrogate, convert to UTF32. */
+		if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END) {
+		    ch = ((ch - UNI_SUR_HIGH_START) << halfShift)
+			+ (ch2 - UNI_SUR_LOW_START) + halfBase;
+		    ++source;
+		} else if (flags == strictConversion) { /* it's an unpaired high surrogate */
+		    --source; /* return to the illegal value itself */
+		    result = sourceIllegal;
+		    break;
+		}
+	    } else { /* We don't have the 16 bits following the high surrogate. */
+		--source; /* return to the high surrogate */
+		result = sourceExhausted;
+		break;
+	    }
+	} else if (flags == strictConversion) {
+	    /* UTF-16 surrogate values are illegal in UTF-32 */
+	    if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END) {
+		--source; /* return to the illegal value itself */
+		result = sourceIllegal;
+		break;
+	    }
+	}
+	if (target >= targetEnd) {
+	    source = oldSource; /* Back up source pointer! */
+	    result = targetExhausted; break;
+	}
+	*target++ = ch;
+    }
+    *sourceStart = source;
+    *targetStart = target;
+#ifdef CVTUTF_DEBUG
+if (result == sourceIllegal) {
+    fprintf(stderr, "ConvertUTF16toUTF32 illegal seq 0x%04x,%04x\n", ch, ch2);
+    fflush(stderr);
+}
+#endif
+    return result;
+}
+
+/* --------------------------------------------------------------------- */
+
+/*
+ * Index into the table below with the first byte of a UTF-8 sequence to
+ * get the number of trailing bytes that are supposed to follow it.
+ * Note that *legal* UTF-8 values can't have 4 or 5-bytes. The table is
+ * left as-is for anyone who may want to do such conversion, which was
+ * allowed in earlier algorithms.
+ */
+static const char trailingBytesForUTF8[256] = {
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
+};
+
+/*
+ * Magic values subtracted from a buffer value during UTF8 conversion.
+ * This table contains as many values as there might be trailing bytes
+ * in a UTF-8 sequence.
+ */
+static const UTF32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL, 
+		     0x03C82080UL, 0xFA082080UL, 0x82082080UL };
+
+/*
+ * Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
+ * into the first byte, depending on how many bytes follow.  There are
+ * as many entries in this table as there are UTF-8 sequence types.
+ * (I.e., one byte sequence, two byte... etc.). Remember that sequencs
+ * for *legal* UTF-8 will be 4 or fewer bytes total.
+ */
+static const UTF8 firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };
+
+/* --------------------------------------------------------------------- */
+
+/* The interface converts a whole buffer to avoid function-call overhead.
+ * Constants have been gathered. Loops & conditionals have been removed as
+ * much as possible for efficiency, in favor of drop-through switches.
+ * (See "Note A" at the bottom of the file for equivalent code.)
+ * If your compiler supports it, the "isLegalUTF8" call can be turned
+ * into an inline function.
+ */
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF16toUTF8 (
+	const UTF16** sourceStart, const UTF16* sourceEnd, 
+	UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF16* source = *sourceStart;
+    UTF8* target = *targetStart;
+    while (source < sourceEnd) {
+	UTF32 ch;
+	unsigned short bytesToWrite = 0;
+	const UTF32 byteMask = 0xBF;
+	const UTF32 byteMark = 0x80; 
+	const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */
+	ch = *source++;
+	/* If we have a surrogate pair, convert to UTF32 first. */
+	if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) {
+	    /* If the 16 bits following the high surrogate are in the source buffer... */
+	    if (source < sourceEnd) {
+		UTF32 ch2 = *source;
+		/* If it's a low surrogate, convert to UTF32. */
+		if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END) {
+		    ch = ((ch - UNI_SUR_HIGH_START) << halfShift)
+			+ (ch2 - UNI_SUR_LOW_START) + halfBase;
+		    ++source;
+		} else if (flags == strictConversion) { /* it's an unpaired high surrogate */
+		    --source; /* return to the illegal value itself */
+		    result = sourceIllegal;
+		    break;
+		}
+	    } else { /* We don't have the 16 bits following the high surrogate. */
+		--source; /* return to the high surrogate */
+		result = sourceExhausted;
+		break;
+	    }
+	} else if (flags == strictConversion) {
+	    /* UTF-16 surrogate values are illegal in UTF-32 */
+	    if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END) {
+		--source; /* return to the illegal value itself */
+		result = sourceIllegal;
+		break;
+	    }
+	}
+	/* Figure out how many bytes the result will require */
+	if (ch < (UTF32)0x80) {	     bytesToWrite = 1;
+	} else if (ch < (UTF32)0x800) {     bytesToWrite = 2;
+	} else if (ch < (UTF32)0x10000) {   bytesToWrite = 3;
+	} else if (ch < (UTF32)0x110000) {  bytesToWrite = 4;
+	} else {			    bytesToWrite = 3;
+					    ch = UNI_REPLACEMENT_CHAR;
+	}
+
+	target += bytesToWrite;
+	if (target > targetEnd) {
+	    source = oldSource; /* Back up source pointer! */
+	    target -= bytesToWrite; result = targetExhausted; break;
+	}
+	switch (bytesToWrite) { /* note: everything falls through. */
+	    case 4: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 1: *--target =  (UTF8)(ch | firstByteMark[bytesToWrite]);
+	}
+	target += bytesToWrite;
+    }
+    *sourceStart = source;
+    *targetStart = target;
+    return result;
+}
+
+/* --------------------------------------------------------------------- */
+
+/*
+ * Utility routine to tell whether a sequence of bytes is legal UTF-8.
+ * This must be called with the length pre-determined by the first byte.
+ * If not calling this from ConvertUTF8to*, then the length can be set by:
+ *  length = trailingBytesForUTF8[*source]+1;
+ * and the sequence is illegal right away if there aren't that many bytes
+ * available.
+ * If presented with a length > 4, this returns false.  The Unicode
+ * definition of UTF-8 goes up to 4-byte sequences.
+ */
+
+static Boolean isLegalUTF8(const UTF8 *source, int length) {
+    UTF8 a;
+    const UTF8 *srcptr = source+length;
+    switch (length) {
+    default: return false;
+	/* Everything else falls through when "true"... */
+    case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
+    case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
+    case 2: if ((a = (*--srcptr)) > 0xBF) return false;
+
+	switch (*source) {
+	    /* no fall-through in this inner switch */
+	    case 0xE0: if (a < 0xA0) return false; break;
+	    case 0xED: if (a > 0x9F) return false; break;
+	    case 0xF0: if (a < 0x90) return false; break;
+	    case 0xF4: if (a > 0x8F) return false; break;
+	    default:   if (a < 0x80) return false;
+	}
+
+    case 1: if (*source >= 0x80 && *source < 0xC2) return false;
+    }
+    if (*source > 0xF4) return false;
+    return true;
+}
+
+/* --------------------------------------------------------------------- */
+
+/*
+ * Exported function to return whether a UTF-8 sequence is legal or not.
+ * This is not used here; it's just exported.
+ */
+Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd) {
+    int length = trailingBytesForUTF8[*source]+1;
+    if (source+length > sourceEnd) {
+	return false;
+    }
+    return isLegalUTF8(source, length);
+}
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF8toUTF16 (
+	const UTF8** sourceStart, const UTF8* sourceEnd, 
+	UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF8* source = *sourceStart;
+    UTF16* target = *targetStart;
+    while (source < sourceEnd) {
+	UTF32 ch = 0;
+	unsigned short extraBytesToRead = trailingBytesForUTF8[*source];
+	if (source + extraBytesToRead >= sourceEnd) {
+	    result = sourceExhausted; break;
+	}
+	/* Do this check whether lenient or strict */
+	if (! isLegalUTF8(source, extraBytesToRead+1)) {
+	    result = sourceIllegal;
+	    break;
+	}
+	/*
+	 * The cases all fall through. See "Note A" below.
+	 */
+	switch (extraBytesToRead) {
+	    case 5: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */
+	    case 4: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */
+	    case 3: ch += *source++; ch <<= 6;
+	    case 2: ch += *source++; ch <<= 6;
+	    case 1: ch += *source++; ch <<= 6;
+	    case 0: ch += *source++;
+	}
+	ch -= offsetsFromUTF8[extraBytesToRead];
+
+	if (target >= targetEnd) {
+	    source -= (extraBytesToRead+1); /* Back up source pointer! */
+	    result = targetExhausted; break;
+	}
+	if (ch <= UNI_MAX_BMP) { /* Target is a character <= 0xFFFF */
+	    /* UTF-16 surrogate values are illegal in UTF-32 */
+	    if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) {
+		if (flags == strictConversion) {
+		    source -= (extraBytesToRead+1); /* return to the illegal value itself */
+		    result = sourceIllegal;
+		    break;
+		} else {
+		    *target++ = UNI_REPLACEMENT_CHAR;
+		}
+	    } else {
+		*target++ = (UTF16)ch; /* normal case */
+	    }
+	} else if (ch > UNI_MAX_UTF16) {
+	    if (flags == strictConversion) {
+		result = sourceIllegal;
+		source -= (extraBytesToRead+1); /* return to the start */
+		break; /* Bail out; shouldn't continue */
+	    } else {
+		*target++ = UNI_REPLACEMENT_CHAR;
+	    }
+	} else {
+	    /* target is a character in range 0xFFFF - 0x10FFFF. */
+	    if (target + 1 >= targetEnd) {
+		source -= (extraBytesToRead+1); /* Back up source pointer! */
+		result = targetExhausted; break;
+	    }
+	    ch -= halfBase;
+	    *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);
+	    *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);
+	}
+    }
+    *sourceStart = source;
+    *targetStart = target;
+    return result;
+}
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF32toUTF8 (
+	const UTF32** sourceStart, const UTF32* sourceEnd, 
+	UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF32* source = *sourceStart;
+    UTF8* target = *targetStart;
+    while (source < sourceEnd) {
+	UTF32 ch;
+	unsigned short bytesToWrite = 0;
+	const UTF32 byteMask = 0xBF;
+	const UTF32 byteMark = 0x80; 
+	ch = *source++;
+	if (flags == strictConversion ) {
+	    /* UTF-16 surrogate values are illegal in UTF-32 */
+	    if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) {
+		--source; /* return to the illegal value itself */
+		result = sourceIllegal;
+		break;
+	    }
+	}
+	/*
+	 * Figure out how many bytes the result will require. Turn any
+	 * illegally large UTF32 things (> Plane 17) into replacement chars.
+	 */
+	if (ch < (UTF32)0x80) {	     bytesToWrite = 1;
+	} else if (ch < (UTF32)0x800) {     bytesToWrite = 2;
+	} else if (ch < (UTF32)0x10000) {   bytesToWrite = 3;
+	} else if (ch <= UNI_MAX_LEGAL_UTF32) {  bytesToWrite = 4;
+	} else {			    bytesToWrite = 3;
+					    ch = UNI_REPLACEMENT_CHAR;
+					    result = sourceIllegal;
+	}
+	
+	target += bytesToWrite;
+	if (target > targetEnd) {
+	    --source; /* Back up source pointer! */
+	    target -= bytesToWrite; result = targetExhausted; break;
+	}
+	switch (bytesToWrite) { /* note: everything falls through. */
+	    case 4: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6;
+	    case 1: *--target = (UTF8) (ch | firstByteMark[bytesToWrite]);
+	}
+	target += bytesToWrite;
+    }
+    *sourceStart = source;
+    *targetStart = target;
+    return result;
+}
+
+/* --------------------------------------------------------------------- */
+
+ConversionResult ConvertUTF8toUTF32 (
+	const UTF8** sourceStart, const UTF8* sourceEnd, 
+	UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags) {
+    ConversionResult result = conversionOK;
+    const UTF8* source = *sourceStart;
+    UTF32* target = *targetStart;
+    while (source < sourceEnd) {
+	UTF32 ch = 0;
+	unsigned short extraBytesToRead = trailingBytesForUTF8[*source];
+	if (source + extraBytesToRead >= sourceEnd) {
+	    result = sourceExhausted; break;
+	}
+	/* Do this check whether lenient or strict */
+	if (! isLegalUTF8(source, extraBytesToRead+1)) {
+	    result = sourceIllegal;
+	    break;
+	}
+	/*
+	 * The cases all fall through. See "Note A" below.
+	 */
+	switch (extraBytesToRead) {
+	    case 5: ch += *source++; ch <<= 6;
+	    case 4: ch += *source++; ch <<= 6;
+	    case 3: ch += *source++; ch <<= 6;
+	    case 2: ch += *source++; ch <<= 6;
+	    case 1: ch += *source++; ch <<= 6;
+	    case 0: ch += *source++;
+	}
+	ch -= offsetsFromUTF8[extraBytesToRead];
+
+	if (target >= targetEnd) {
+	    source -= (extraBytesToRead+1); /* Back up the source pointer! */
+	    result = targetExhausted; break;
+	}
+	if (ch <= UNI_MAX_LEGAL_UTF32) {
+	    /*
+	     * UTF-16 surrogate values are illegal in UTF-32, and anything
+	     * over Plane 17 (> 0x10FFFF) is illegal.
+	     */
+	    if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END) {
+		if (flags == strictConversion) {
+		    source -= (extraBytesToRead+1); /* return to the illegal value itself */
+		    result = sourceIllegal;
+		    break;
+		} else {
+		    *target++ = UNI_REPLACEMENT_CHAR;
+		}
+	    } else {
+		*target++ = ch;
+	    }
+	} else { /* i.e., ch > UNI_MAX_LEGAL_UTF32 */
+	    result = sourceIllegal;
+	    *target++ = UNI_REPLACEMENT_CHAR;
+	}
+    }
+    *sourceStart = source;
+    *targetStart = target;
+    return result;
+}
+
+/* ---------------------------------------------------------------------
+
+    Note A.
+    The fall-through switches in UTF-8 reading code save a
+    temp variable, some decrements & conditionals.  The switches
+    are equivalent to the following loop:
+	{
+	    int tmpBytesToRead = extraBytesToRead+1;
+	    do {
+		ch += *source++;
+		--tmpBytesToRead;
+		if (tmpBytesToRead) ch <<= 6;
+	    } while (tmpBytesToRead > 0);
+	}
+    In UTF-8 writing code, the switches on "bytesToWrite" are
+    similarly unrolled loops.
+
+   --------------------------------------------------------------------- */