| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Control operators, after Simon Tatham |
| 4 | * |
| 5 | * (c) 2022 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of the mLib utilities library. |
| 11 | * |
| 12 | * mLib is free software: you can redistribute it and/or modify it under |
| 13 | * the terms of the GNU Library General Public License as published by |
| 14 | * the Free Software Foundation; either version 2 of the License, or (at |
| 15 | * your option) any later version. |
| 16 | * |
| 17 | * mLib is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
| 20 | * License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with mLib. If not, write to the Free Software |
| 24 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
| 25 | * USA. |
| 26 | */ |
| 27 | |
| 28 | #ifndef MLIB_CONTROL_H |
| 29 | #define MLIB_CONTROL_H |
| 30 | |
| 31 | #ifdef __cplusplus |
| 32 | extern "C" { |
| 33 | #endif |
| 34 | |
| 35 | /*----- Header files ------------------------------------------------------*/ |
| 36 | |
| 37 | #ifndef MLIB_MACROS_H |
| 38 | # include "macros.h" |
| 39 | #endif |
| 40 | |
| 41 | /*----- Macros provided ---------------------------------------------------*/ |
| 42 | |
| 43 | /* @MCTRL__LABEL(tag)@ * |
| 44 | * |
| 45 | * Expand to a plausibly unique label based on the current line number and |
| 46 | * the @tag@. |
| 47 | */ |
| 48 | #define MCTRL__LABEL(tag) GLUE(_mctrl__##tag##__, __LINE__) |
| 49 | |
| 50 | /* @FIRSTBRANCH(tag_0) stmt_0@ |
| 51 | * [@MIDBRANCH(tag_i) stmt_i ...@] |
| 52 | * @LASTBRANCH(tag_n) stmt_n@ |
| 53 | * @GOBRANCH(tag);@ |
| 54 | * |
| 55 | * If control enters at the top, then only <stmt_0> is executed, followed by |
| 56 | * the statement after. Following @GOBRANCH(tag)@, control continues |
| 57 | * from the correspondingly tagged statement, and continues with the |
| 58 | * following statement again. |
| 59 | */ |
| 60 | #define FIRSTBRANCH(tag) if (1) { goto MCTRL__LABEL(tag); MCTRL__LABEL(tag): |
| 61 | #define MIDBRANCH(tag) } else if (0) MCTRL__LABEL(tag): { |
| 62 | #define LASTBRANCH(tag) } else MCTRL__LABEL(tag): |
| 63 | #define GOBRANCH(tag) goto MCTRL__LABEL(tag) |
| 64 | |
| 65 | /* @BEFORE(tag, stmt_0) stmt_1@ |
| 66 | * |
| 67 | * Execute @stmt_0@ and then @stmt_1@. |
| 68 | */ |
| 69 | #define BEFORE(tag, stmt) \ |
| 70 | if (1) { stmt goto MCTRL__LABEL(tag##__before_body); } \ |
| 71 | else MCTRL__LABEL(tag##__before_body): |
| 72 | |
| 73 | /* @AFTER(tag, stmt_0) stmt_1@ |
| 74 | * |
| 75 | * Execute @stmt_1@ and then @stmt_0@. If either statement invokes @break@ |
| 76 | * then control immediately transfers to the statement following @AFTER@. If |
| 77 | * either invokes @continue@, then control returns to @stmt_0@. |
| 78 | */ |
| 79 | #define AFTER(tag, stmt) \ |
| 80 | if (1) goto MCTRL__LABEL(tag##__after_body); \ |
| 81 | else if (1) { MCTRL__LABEL(tag##__after_end): stmt } \ |
| 82 | else for (;;) \ |
| 83 | if (1) goto MCTRL__LABEL(tag##__after_end); \ |
| 84 | else MCTRL__LABEL(tag##__after_body): |
| 85 | |
| 86 | /* @WRAP(tag, before, onend, onbreak) stmt@ |
| 87 | * |
| 88 | * Execute the @before@ statement, followed by @stmt@. If @stmt@ invokes |
| 89 | * @break@, then @onbreak@ is immediately executed; if @stmt@ completes |
| 90 | * normally, or invokes @continue@ then @onend@ is immediately executed. |
| 91 | * Any @break@ and @continue@ in the @before@, @onend@, and @onbreak@ |
| 92 | * statements behave as one would expect from their context. |
| 93 | */ |
| 94 | #define WRAP(tag, before, onend, onbreak) \ |
| 95 | if (1) { before goto MCTRL__LABEL(tag##__wrap_body); } \ |
| 96 | else if (1) { MCTRL__LABEL(tag##__wrap_end): onend } \ |
| 97 | else if (1) { MCTRL__LABEL(tag##__wrap_break): onbreak } \ |
| 98 | else for (;;) \ |
| 99 | if (1) goto MCTRL__LABEL(tag##__wrap_break); \ |
| 100 | else for (;;) \ |
| 101 | if (1) goto MCTRL__LABEL(tag##__wrap_end); \ |
| 102 | else MCTRL__LABEL(tag##__wrap_body): |
| 103 | |
| 104 | /* @ALLOWELSE(tag, before, onend, onbreak) stmt_0 [else stmt_1]@ |
| 105 | * @GOELSE(tag);@ |
| 106 | * |
| 107 | * Execute the @before@ statement, followed by @stmt_0@. If @stmt_0@ |
| 108 | * completes, or invokes @break@ or @continue@, then control continues with |
| 109 | * the next statement. If @GOELSE(tag)@ is invoked anywhere in the |
| 110 | * function, then @before@ is executed, followed by @stmt_1@ (if present). |
| 111 | * If @stmt_1@ invokes @break@ then control passes to @onbreak@; if @stmt_1@ |
| 112 | * ends normally then control passes to @onend@. Any @break@ and @continue@ |
| 113 | * in the @before@, @onend@, and @onbreak@ statements behave as one would |
| 114 | * expect from their context. |
| 115 | */ |
| 116 | #define ALLOWELSE(tag, before, onend, onbreak) \ |
| 117 | if (1) goto MCTRL__LABEL(tag##__allowelse_body); \ |
| 118 | else if (1) MCTRL__LABEL(tag##__allowelse_body_end): ; \ |
| 119 | else if (1) { MCTRL__LABEL(tag##__allowelse_else_end): onend } \ |
| 120 | else if (1) { MCTRL__LABEL(tag##__allowelse_else_break): onbreak } \ |
| 121 | else if (1) { \ |
| 122 | MCTRL__LABEL(tag##__allowelse_before_else): \ |
| 123 | before goto MCTRL__LABEL(tag##__allowelse_else); \ |
| 124 | } else for (;;) \ |
| 125 | if (1) goto MCTRL__LABEL(tag##__allowelse_else_break); \ |
| 126 | else for (;;) \ |
| 127 | if (1) goto MCTRL__LABEL(tag##__allowelse_else_end); \ |
| 128 | else MCTRL__LABEL(tag##__allowelse_else): if (0) for (;;) \ |
| 129 | if (1) goto MCTRL__LABEL(tag##__allowelse_body_end); \ |
| 130 | else MCTRL__LABEL(tag##__allowelse_body): |
| 131 | #define GOELSE(tag) \ |
| 132 | goto MCTRL__LABEL(tag##__allowelse_before_else) |
| 133 | |
| 134 | /* @DOWHILE(tag, cond) stmt@ |
| 135 | * |
| 136 | * Repeatedly execute @stmt@ until @cond@ evaluates to zero. Execute @stmt@ |
| 137 | * at least once. The @break@ and @continue@ statements work within @stmt@ |
| 138 | * as one would expect. |
| 139 | */ |
| 140 | #define DOWHILE(tag, cond) \ |
| 141 | if (1) goto MCTRL__LABEL(tag##__dowhile_body); \ |
| 142 | else while (cond) MCTRL__LABEL(tag##__dowhile_body): |
| 143 | |
| 144 | /* @DECL(tag, decl) stmt@ |
| 145 | * |
| 146 | * Execute @stmt@ with @decl@ in scope. If @stmt@ completes or invokes |
| 147 | * @break@ or @continue@ then control continues with the statement following |
| 148 | * @DECL@. Internally, this uses @for@, so it only works in C99 or later, or |
| 149 | * C++. |
| 150 | */ |
| 151 | #if __STDC_VERSION__ >= 199901 || defined(__cplusplus) |
| 152 | # define DECL(tag, decl) \ |
| 153 | for (decl;;) \ |
| 154 | if (1) goto MCTRL__LABEL(tag##__decl_body); \ |
| 155 | else if (1) MCTRL__LABEL(tag##__decl_exit): break; \ |
| 156 | else for (;;) \ |
| 157 | if (1) goto MCTRL__LABEL(tag##__decl_exit); \ |
| 158 | else MCTRL__LABEL(tag##__decl_body): |
| 159 | #endif |
| 160 | |
| 161 | /*----- That's all, folks -------------------------------------------------*/ |
| 162 | |
| 163 | #ifdef __cplusplus |
| 164 | } |
| 165 | #endif |
| 166 | |
| 167 | #endif |