72 lines
1.8 KiB
C
72 lines
1.8 KiB
C
/*
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* nanowasm, a tiny WebAssembly/Wasm interpreter
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* Copyright (C) 2023-2024 Xavier Del Campo Romero
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/.
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*/
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#include <nw/leb128.h>
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#include <nw/log.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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/* The functions below are (somewhat heavily) modified versions of those
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* provided by the wac project: https://github.com/kanaka/wac */
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/*
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* Copyright (C) Joel Martin <github@martintribe.org>
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* The wac project is licensed under the MPL 2.0 (Mozilla Public License
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* 2.0). The text of the MPL 2.0 license is included below and can be
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* found at https://www.mozilla.org/MPL/2.0/
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*/
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static int read_LEB(FILE *const f, const unsigned maxbits,
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const bool sign, unsigned long long *const out)
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{
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unsigned long long result = 0;
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unsigned shift = 0, bcnt = 0;
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uint8_t byte;
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for (;;)
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{
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if (!fread(&byte, sizeof byte, 1, f))
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return -1;
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result |= (unsigned long long)(byte & 0x7f) << shift;
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shift += 7;
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if (!(byte & 0x80))
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break;
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else if (++bcnt > (maxbits + 7 - 1) / 7)
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{
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LOG("%s: overflow\n", __func__);
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return -1;
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}
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}
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if (sign && (shift < maxbits) && (byte & 0x40))
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result |= -1ll << shift;
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*out = result;
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return 0;
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}
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int leb128_read_unsigned(FILE *const f, const unsigned maxbits,
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unsigned long long *const out)
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{
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return read_LEB(f, maxbits, false, out);
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}
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int leb128_read_signed(FILE *const f, const unsigned maxbits,
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long long *const out)
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{
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unsigned long long value;
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const int ret = read_LEB(f, maxbits, true, &value);
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*out = value;
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return ret;
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}
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