src/common/convert_UTF.h

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#ifndef COMMON_CONVERT_UTF_H_
#define COMMON_CONVERT_UTF_H_

/* ---------------------------------------------------------------------

Conversions between UTF32, UTF-16, and UTF-8.  Header file.

Several funtions are included here, forming a complete set of
conversions between the three formats.  UTF-7 is not included
here, but is handled in a separate source file.

Each of these routines takes pointers to input buffers and output
buffers.  The input buffers are const.

Each routine converts the text between *sourceStart and sourceEnd,
putting the result into the buffer between *targetStart and
targetEnd. Note: the end pointers are *after* the last item: e.g.
*(sourceEnd - 1) is the last item.

The return result indicates whether the conversion was successful,
and if not, whether the problem was in the source or target buffers.
(Only the first encountered problem is indicated.)

After the conversion, *sourceStart and *targetStart are both
updated to point to the end of last text successfully converted in
the respective buffers.

Input parameters:
sourceStart - pointer to a pointer to the source buffer.
The contents of this are modified on return so that
it points at the next thing to be converted.
targetStart - similarly, pointer to pointer to the target buffer.
sourceEnd, targetEnd - respectively pointers to the ends of the
two buffers, for overflow checking only.

These conversion functions take a ConversionFlags argument. When this
flag is set to strict, both irregular sequences and isolated surrogates
will cause an error.  When the flag is set to lenient, both irregular
sequences and isolated surrogates are converted.

Whether the flag is strict or lenient, all illegal sequences will cause
an error return. This includes sequences such as: <F4 90 80 80>, <C0 80>,
or <A0> in UTF-8, and values above 0x10FFFF in UTF-32. Conformant code
must check for illegal sequences.

When the flag is set to lenient, characters over 0x10FFFF are converted
to the replacement character; otherwise (when the flag is set to strict)
they constitute an error.

Output parameters:
The value "sourceIllegal" is returned from some routines if the input
sequence is malformed.  When "sourceIllegal" is returned, the source
value will point to the illegal value that caused the problem. E.g.,
in UTF-8 when a sequence is malformed, it points to the start of the
malformed sequence.

Author: Mark E. Davis, 1994.
Rev History: Rick McGowan, fixes & updates May 2001.
Fixes & updates, Sept 2001.

------------------------------------------------------------------------ */

/* ---------------------------------------------------------------------
The following 4 definitions are compiler-specific.
The C standard does not guarantee that wchar_t has at least
16 bits, so wchar_t is no less portable than unsigned short!
All should be unsigned values to avoid sign extension during
bit mask & shift operations.
------------------------------------------------------------------------ */

typedef unsigned long	UTF32;	/* at least 32 bits */
typedef unsigned short	UTF16;	/* at least 16 bits */
typedef unsigned char	UTF8;	/* typically 8 bits */
typedef unsigned char	Boolean; /* 0 or 1 */

/* Some fundamental constants */
#define UNI_REPLACEMENT_CHAR (UTF32)0x0000FFFD
#define UNI_MAX_BMP (UTF32)0x0000FFFF
#define UNI_MAX_UTF16 (UTF32)0x0010FFFF
#define UNI_MAX_UTF32 (UTF32)0x7FFFFFFF
#define UNI_MAX_LEGAL_UTF32 (UTF32)0x0010FFFF

typedef enum {
	conversionOK, 		/* conversion successful */
	sourceExhausted,	/* partial character in source, but hit end */
	targetExhausted,	/* insuff. room in target for conversion */
	sourceIllegal		/* source sequence is illegal/malformed */
} ConversionResult;

typedef enum {
	strictConversion = 0,
	lenientConversion
} ConversionFlags;

/* This is for C++ and does no harm in C */
#ifdef __cplusplus
extern "C" {
#endif

ConversionResult ConvertUTF8toUTF16 (const UTF8** sourceStart, const UTF8* sourceEnd,
                                     UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags);

ConversionResult ConvertUTF16toUTF8 (const UTF16** sourceStart, const UTF16* sourceEnd,
                                     UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags);

ConversionResult ConvertUTF8toUTF32 (const UTF8** sourceStart, const UTF8* sourceEnd,
                                     UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags);

ConversionResult ConvertUTF32toUTF8 (const UTF32** sourceStart, const UTF32* sourceEnd,
                                     UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags);

ConversionResult ConvertUTF16toUTF32 (const UTF16** sourceStart, const UTF16* sourceEnd,
                                      UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags);

ConversionResult ConvertUTF32toUTF16 (const UTF32** sourceStart, const UTF32* sourceEnd,
                                      UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags);

Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd);

#ifdef __cplusplus
}
#endif

/* --------------------------------------------------------------------- */

#endif  // COMMON_CONVERT_UTF_H_