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Up-to-date trunk clang has introduced a built-in operator called _Countof, which is like the 'lenof' macro in this code (returns the number of elements in a statically-declared array object) but with the safety advantage that it provokes a compile error if you accidentally use it on a pointer. In this commit I add a cmake-time check for it, and conditional on that, switch over the definition of lenof. This should add a safety check for accidental uses of lenof(pointer). When I tested it with new clang, this whole code base compiled cleanly with the new setting, so there aren't currently any such accidents. clang cites C2y as the source for _Countof: WG14 document N3369 initially proposed it under a different name, and then there was a big internet survey about naming (in which of course I voted for lenof!), and document N3469 summarises the results, which show that the name _Countof and/or countof won. Links: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3369.pdf https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3469.htm My reading of N3469 seems to say that there will _either_ be _Countof by itself, _or_ lowercase 'countof' as a new keyword, but they don't say which. They say they _don't_ intend to do the same equivocation we had with _Complex and _Bool, where you have a _Countof keyword and an optional header file defining a lowercase non-underscore macro wrapping it. But there hasn't been a new whole draft published since N3469 yet, so I don't know what will end up in it when there is. However, as of now, _Countof exists in at least one compiler, and that seems like enough reason to implement it here. If it becomes 'countof' in the real standard, then we can always change over later. (And in that case it would probably make sense to rename the macro throughout the code base to align with what will become the new standard usage.)
96 lines
3.2 KiB
C
96 lines
3.2 KiB
C
/*
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* internal.h - internal header stuff for the charset library.
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*/
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#ifndef charset_internal_h
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#define charset_internal_h
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/* This invariably comes in handy */
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#ifndef lenof
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#if HAVE_COUNTOF
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#define lenof(x) _Countof(x)
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#else
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#define lenof(x) ( (sizeof((x))) / (sizeof(*(x))))
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#endif
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#endif
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/* This is an invalid Unicode value used to indicate an error. */
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#define ERROR 0xFFFFL /* Unicode value representing error */
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typedef struct charset_spec charset_spec;
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typedef struct sbcs_data sbcs_data;
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struct charset_spec {
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int charset; /* numeric identifier */
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/*
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* A function to read the character set and output Unicode
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* characters. The `emit' function expects to get Unicode chars
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* passed to it; it should be sent ERROR for any encoding error
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* on the input.
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*/
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void (*read)(charset_spec const *charset, long int input_chr,
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charset_state *state,
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void (*emit)(void *ctx, long int output), void *emitctx);
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/*
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* A function to read Unicode characters and output in this
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* character set. The `emit' function expects to get byte
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* values passed to it; it should be sent ERROR for any
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* non-representable characters on the input.
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*/
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void (*write)(charset_spec const *charset, long int input_chr,
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charset_state *state,
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void (*emit)(void *ctx, long int output), void *emitctx);
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void const *data;
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};
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/*
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* This is the format of `data' used by the SBCS read and write
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* functions; so it's the format used in all SBCS definitions.
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*/
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struct sbcs_data {
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/*
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* This is a simple mapping table converting each SBCS position
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* to a Unicode code point. Some positions may contain ERROR,
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* indicating that that byte value is not defined in the SBCS
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* in question and its occurrence in input is an error.
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*/
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unsigned long sbcs2ucs[256];
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/*
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* This lookup table is used to convert Unicode back to the
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* SBCS. It consists of the valid byte values in the SBCS,
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* sorted in order of their Unicode translation. So given a
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* Unicode value U, you can do a binary search on this table
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* using the above table as a lookup: when testing the Xth
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* position in this table, you branch according to whether
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* sbcs2ucs[ucs2sbcs[X]] is less than, greater than, or equal
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* to U.
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*
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* Note that since there may be fewer than 256 valid byte
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* values in a particular SBCS, we must supply the length of
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* this table as well as the contents.
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*/
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unsigned char ucs2sbcs[256];
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int nvalid;
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};
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/*
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* Prototypes for internal library functions.
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*/
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charset_spec const *charset_find_spec(int charset);
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void read_sbcs(charset_spec const *charset, long int input_chr,
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charset_state *state,
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void (*emit)(void *ctx, long int output), void *emitctx);
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void write_sbcs(charset_spec const *charset, long int input_chr,
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charset_state *state,
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void (*emit)(void *ctx, long int output), void *emitctx);
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/*
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* Placate compiler warning about unused parameters, of which we
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* expect to have some in this library.
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*/
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#define UNUSEDARG(x) ( (x) = (x) )
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#endif /* charset_internal_h */
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