152 lines
5.2 KiB
C
152 lines
5.2 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_`, `BOX`, and `BOX_CONTENT`.
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@param[STR_(n)]
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A one-argument macro producing a name that is responsible for the name of the
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to string function. Should be something like
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`STR_(to_string) -> widget_foo_to_string`. The caller is responsible for
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undefining `STR_`.
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@param[TO_STRING]
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Function implementing <typedef:<PZ>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_) || !defined(BOX) || !defined(BOX_CONTENT) \
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|| !defined(STR_) || !defined(TO_STRING)
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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 defines.
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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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typedef BOX PSTR_(box);
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typedef BOX_CONTENT PSTR_(element_c);
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/** <src/to_string.h>: responsible for turning the argument into a 12-`char`
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null-terminated output string. */
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typedef void (*PSTR_(to_string_fn))(PSTR_(element_c), char (*)[12]);
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/* Check that `TO_STRING` is a function implementing
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<typedef:<PSTR>to_string>. */
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static const PSTR_(to_string_fn) PSTR_(to_string) = (TO_STRING);
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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. `<STR>` is
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loosely contracted to be a name `<X>box[<X_TO_STRING_NAME>]`.
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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_c) x;
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struct BOX_(forward) 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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it = BOX_(forward_begin)(box);
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*b++ = left;
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while(BOX_(is_element_c)(x = BOX_(forward_next)(&it))) {
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PSTR_(to_string)(x, (char (*)[12])b);
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/* Paranoid about '\0'. */
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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_c)(BOX_(forward_next)(&it))) goto ellipsis;
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else break;
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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 TO_STRING
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#ifdef TO_STRING_NAME
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#undef TO_STRING_NAME
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#endif
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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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