172 lines
6.1 KiB
C
172 lines
6.1 KiB
C
/* @license 2020 Neil Edelman, distributed under the terms of the
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[MIT License](https://opensource.org/licenses/MIT).
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@subtitle To string trait
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Interface defined by box. Requires `<NAME>[_<TRAIT>]_to_string` be declared as
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a <typedef:<PSTR>to_string_fn>.
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@param[TO_STRING_LEFT, TO_STRING_RIGHT]
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7-bit characters, defaults to '(' and ')'.
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@param[TO_STRING_EXTERN, TO_STRING_INTERN]
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Normally the space to put the temporary strings is static, one per file. With
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this, it's possible to have a global storage to save space: have one file have
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`TO_STRING_INTERN` as the first box, the other files `TO_STRING_EXTERN`. This
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is unsynchronized.
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@fixme `extern` untested.
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@std C89 */
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#if !defined(BOX_TYPE) || !defined(BOX_CONTENT) || !defined(BOX_) \
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|| !defined(BOX_MAJOR_NAME) || !defined(BOX_MINOR_NAME) \
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|| defined(STR_) || defined(STREXTERN_)
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#error Unexpected preprocessor symbols.
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#endif
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#if defined(TO_STRING_H) \
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&& (defined(TO_STRING_EXTERN) || defined(TO_STRING_INTERN)) /* <!-- not */
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#error Should be the on the first to_string in the compilation unit.
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#else /* not --><!-- !not */
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#if defined(TO_STRING_EXTERN) && defined(TO_STRING_INTERN) /* <!-- two */
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#error These can not be defined together.
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#endif /* two --> */
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#endif /* !not --> */
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#ifndef TO_STRING_H /* <!-- idempotent */
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#define TO_STRING_H
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#include <string.h>
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#if defined(TO_STRING_CAT_) || defined(TO_STRING_CAT) || defined(PSTR_)
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#error Unexpected preprocessor symbols.
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#endif
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/* <Kernighan and Ritchie, 1988, p. 231>. */
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#define TO_STRING_CAT_(n, m) n ## _ ## m
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#define TO_STRING_CAT(n, m) TO_STRING_CAT_(n, m)
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#define PSTR_(n) TO_STRING_CAT(to_string, STR_(n))
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#if defined(TO_STRING_EXTERN) || defined(TO_STRING_INTERN) /* <!-- ntern */
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extern char to_string_buffers[4][256];
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extern const unsigned to_string_buffers_no;
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extern unsigned to_string_i;
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#ifdef TO_STRING_INTERN /* <!-- intern */
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char to_string_buffers[4][256];
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const unsigned to_string_buffers_no = sizeof to_string_buffers
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/ sizeof *to_string_buffers, to_string_buffer_size
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= sizeof *to_string_buffers / sizeof **to_string_buffers;
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unsigned to_string_buffer_i;
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#endif /* intern --> */
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#else /* ntern --><!-- static */
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static char to_string_buffers[4][256];
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static const unsigned to_string_buffers_no = sizeof to_string_buffers
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/ sizeof *to_string_buffers, to_string_buffer_size
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= sizeof *to_string_buffers / sizeof **to_string_buffers;
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static unsigned to_string_buffer_i;
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#endif /* static --> */
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#endif /* idempotent --> */
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#ifndef TO_STRING_LEFT
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#define TO_STRING_LEFT '('
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#endif
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#ifndef TO_STRING_RIGHT
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#define TO_STRING_RIGHT ')'
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#endif
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#ifndef BOX_TRAIT_NAME /* <!-- !trait */
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#define STR_(n) TO_STRING_CAT(TO_STRING_CAT(BOX_MINOR_NAME, BOX_MAJOR_NAME), n)
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#define STREXTERN_(n) TO_STRING_CAT(BOX_MINOR_NAME, n)
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#else /* !trait --><!-- trait */
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#define STR_(n) TO_STRING_CAT(TO_STRING_CAT(BOX_MINOR_NAME, BOX_MAJOR_NAME), \
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TO_STRING_CAT(BOX_TRAIT_NAME, n))
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#define STREXTERN_(n) TO_STRING_CAT(TO_STRING_CAT(BOX_MINOR_NAME, \
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BOX_TRAIT_NAME), n)
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#endif /* trait --> */
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/* Provides an extra level of indirection for boxes if they need it. */
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#ifndef TO_STRING_THUNK_
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#define TO_STRING_THUNK_(n) n
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#endif
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/* Hopefully gets rid of any nestled-qualifiers, but only when appropriate. */
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#ifndef TO_STRING_CAST
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#define TO_STRING_CAST (void *)
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#endif
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typedef BOX_TYPE PSTR_(box);
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typedef BOX_CONTENT PSTR_(element);
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typedef const BOX_CONTENT PSTR_(element_c); /* Assumes a lot. */
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/** <src/to_string.h>: responsible for turning the read-only argument into a
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12-`char` null-terminated output string. The first argument should be a
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read-only reference to an element and the second a pointer to the bytes. */
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typedef void (*PSTR_(to_string_fn))(const PSTR_(element), char (*)[12]);
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/* _Nb_: this is for documentation only; there is no way to get a general
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read-only type which what we are supplied. Think of nested pointers. */
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/** <src/to_string.h>: print the contents of `box` in a static string buffer of
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256 bytes, with limitations of only printing 4 things at a time.
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@return Address of the static buffer. @order \Theta(1) @allow */
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static const char *STR_(to_string)(const PSTR_(box) *const box) {
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const char comma = ',', space = ' ', ellipsis[] = "…",
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left = TO_STRING_LEFT, right = TO_STRING_RIGHT;
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const size_t ellipsis_len = sizeof ellipsis - 1;
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char *const buffer = to_string_buffers[to_string_buffer_i++], *b = buffer;
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size_t advance;
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PSTR_(element) x;
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struct BOX_(iterator) it;
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int is_sep = 0;
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/* Minimum size: "(" "XXXXXXXXXXX" "," "…" ")" "\0". */
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assert(box && !(to_string_buffers_no & (to_string_buffers_no - 1))
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&& to_string_buffer_size >= 1 + 11 + 1 + ellipsis_len + 1 + 1);
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/* Advance the buffer for next time. */
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to_string_buffer_i &= to_string_buffers_no - 1;
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{ /* We do not modify `box`, but the compiler doesn't know that. */
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PSTR_(box) *promise_box;
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memcpy(&promise_box, &box, sizeof box);
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it = BOX_(iterator)(promise_box);
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}
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*b++ = left;
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while(BOX_(is_element)(x = BOX_(next)(&it))) {
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/* One must have this function declared! */
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TO_STRING_THUNK_(STREXTERN_(to_string))(TO_STRING_CAST
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x, (char (*)[12])b);
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/* Paranoid about '\0'; wastes 1 byte of 12, but otherwise confusing. */
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for(advance = 0; *b != '\0' && advance < 11; b++, advance++);
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is_sep = 1, *b++ = comma, *b++ = space;
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/* Greedy typesetting: enough for "XXXXXXXXXXX" "," "…" ")" "\0". */
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if((size_t)(b - buffer)
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> to_string_buffer_size - 11 - 1 - ellipsis_len - 1 - 1) {
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if(BOX_(is_element)(BOX_(next)(&it))) goto ellipsis;
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else break;
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}
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}
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if(is_sep) b -= 2;
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*b++ = right;
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goto terminate;
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ellipsis:
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b--;
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memcpy(b, ellipsis, ellipsis_len), b += ellipsis_len;
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*b++ = right;
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terminate:
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*b++ = '\0';
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assert(b - buffer <= to_string_buffer_size);
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return buffer;
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}
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static void PSTR_(unused_to_string_coda)(void);
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static void PSTR_(unused_to_string)(void)
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{ STR_(to_string)(0); PSTR_(unused_to_string_coda)(); }
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static void PSTR_(unused_to_string_coda)(void) { PSTR_(unused_to_string)(); }
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#undef STR_
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#undef STREXTERN_
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#undef TO_STRING_CAST
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#undef TO_STRING_THUNK_
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#ifdef TO_STRING_EXTERN
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#undef TO_STRING_EXTERN
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#endif
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#ifdef TO_STRING_INTERN
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#undef TO_STRING_INTERN
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#endif
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#undef TO_STRING_LEFT
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#undef TO_STRING_RIGHT
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