diff options
Diffstat (limited to 'leb128.c')
| -rw-r--r-- | leb128.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/leb128.c b/leb128.c new file mode 100644 index 0000000..c1584c5 --- /dev/null +++ b/leb128.c @@ -0,0 +1,165 @@ +/* + * nwc, a NanoWasm compiler + * Copyright (C) 2025 Xavier Del Campo Romero + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +/* + * Adapted from: + * + * nanowasm, a tiny WebAssembly/Wasm interpreter + * Copyright (C) 2023-2024 Xavier Del Campo Romero + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at https://mozilla.org/MPL/2.0/. + * + * Which, in turn, was adapted from the wac project: + * https://github.com/kanaka/wac + * + * Copyright (C) Joel Martin <github@martintribe.org> + * The wac project is licensed under the MPL 2.0 (Mozilla Public License + * 2.0). The text of the MPL 2.0 license is included below and can be + * found at https://www.mozilla.org/MPL/2.0/ + */ + +#include "types.h" +#include <stdbool.h> +#include <stdint.h> +#include <stdio.h> + +static int read_leb128(FILE *const f, const unsigned maxbits, const bool sign, + unsigned long long *const out) +{ + uint8_t byte; + unsigned long long result = 0; + unsigned shift = 0, bcnt = 0; + + for (;;) + { + if (!fread(&byte, sizeof byte, 1, f)) + { + if (ferror(f)) + fprintf(stderr, "%s: ferror\n", __func__); + + return -1; + } + + result |= (unsigned long long)(byte & 0x7f) << shift; + shift += 7; + + if (!(byte & 0x80)) + break; + else if (++bcnt > (maxbits + 7u - 1u) / 7u) + { + fprintf(stderr, "%s: overflow\n", __func__); + return -1; + } + } + + if (sign && (shift < maxbits) && (byte & 0x40)) + result |= -1ll << shift; + + *out = result; + return 0; +} + +int read_varint1(FILE *const f, varint1 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 1, true, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varint7(FILE *const f, varint7 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 7, true, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varint32(FILE *const f, varint32 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 32, true, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varint64(FILE *const f, varint64 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 64, true, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varuint1(FILE *const f, varuint1 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 1, false, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varuint7(FILE *const f, varuint7 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 7, false, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varuint32(FILE *const f, varuint32 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 32, false, &res)) + return -1; + + *out = res; + return 0; +} + +int read_varuint64(FILE *const f, varuint64 *const out) +{ + unsigned long long res; + + if (read_leb128(f, 64, false, &res)) + return -1; + + *out = res; + return 0; +} |