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128 lines
4.1 KiB
C
128 lines
4.1 KiB
C
/*
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* Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#ifndef OSSL_INTERNAL_QUIC_VLINT_H
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# define OSSL_INTERNAL_QUIC_VLINT_H
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# pragma once
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# include "internal/e_os.h"
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# ifndef OPENSSL_NO_QUIC
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/* The smallest value requiring a 1, 2, 4, or 8-byte representation. */
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#define OSSL_QUIC_VLINT_1B_MIN 0
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#define OSSL_QUIC_VLINT_2B_MIN 64
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#define OSSL_QUIC_VLINT_4B_MIN 16384
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#define OSSL_QUIC_VLINT_8B_MIN 1073741824
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/* The largest value representable in a given number of bytes. */
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#define OSSL_QUIC_VLINT_1B_MAX (OSSL_QUIC_VLINT_2B_MIN - 1)
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#define OSSL_QUIC_VLINT_2B_MAX (OSSL_QUIC_VLINT_4B_MIN - 1)
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#define OSSL_QUIC_VLINT_4B_MAX (OSSL_QUIC_VLINT_8B_MIN - 1)
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#define OSSL_QUIC_VLINT_8B_MAX (((uint64_t)1 << 62) - 1)
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/* The largest value representable as a variable-length integer. */
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#define OSSL_QUIC_VLINT_MAX OSSL_QUIC_VLINT_8B_MAX
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/*
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* Returns the number of bytes needed to encode v in the QUIC variable-length
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* integer encoding.
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*
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* Returns 0 if v exceeds OSSL_QUIC_VLINT_MAX.
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*/
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static ossl_unused ossl_inline size_t ossl_quic_vlint_encode_len(uint64_t v)
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{
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if (v < OSSL_QUIC_VLINT_2B_MIN)
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return 1;
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if (v < OSSL_QUIC_VLINT_4B_MIN)
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return 2;
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if (v < OSSL_QUIC_VLINT_8B_MIN)
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return 4;
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if (v <= OSSL_QUIC_VLINT_MAX)
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return 8;
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return 0;
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}
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/*
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* This function writes a QUIC varable-length encoded integer to buf.
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* The smallest usable representation is used.
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*
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* It is the caller's responsibility to ensure that the buffer is big enough by
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* calling ossl_quic_vlint_encode_len(v) before calling this function.
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*
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* Precondition: buf is at least ossl_quic_vlint_enc_len(v) bytes in size
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* (unchecked)
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* Precondition: v does not exceed OSSL_QUIC_VLINT_MAX
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* (unchecked)
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*/
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void ossl_quic_vlint_encode(unsigned char *buf, uint64_t v);
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/*
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* This function writes a QUIC variable-length encoded integer to buf. The
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* specified number of bytes n are used for the encoding, which means that the
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* encoded value may take up more space than necessary.
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*
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* It is the caller's responsibility to ensure that the buffer is of at least n
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* bytes, and that v is representable by a n-byte QUIC variable-length integer.
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* The representable ranges are:
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*
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* 1-byte encoding: [0, 2** 6-1]
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* 2-byte encoding: [0, 2**14-1]
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* 4-byte encoding: [0, 2**30-1]
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* 8-byte encoding: [0, 2**62-1]
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*
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* Precondition: buf is at least n bytes in size (unchecked)
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* Precondition: v does not exceed the representable range
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* (ossl_quic_vlint_encode_len(v) <= n) (unchecked)
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* Precondition: v does not exceed OSSL_QUIC_VLINT_MAX
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* (unchecked)
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*/
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void ossl_quic_vlint_encode_n(unsigned char *buf, uint64_t v, int n);
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/*
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* Given the first byte of an encoded QUIC variable-length integer, returns
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* the number of bytes comprising the encoded integer, including the first
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* byte.
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*/
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static ossl_unused ossl_inline size_t ossl_quic_vlint_decode_len(uint8_t first_byte)
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{
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return 1U << ((first_byte & 0xC0) >> 6);
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}
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/*
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* Given a buffer containing an encoded QUIC variable-length integer, returns
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* the decoded value. The buffer must be of at least
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* ossl_quic_vlint_decode_len(buf[0]) bytes in size, and the caller is responsible
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* for checking this.
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*
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* Precondition: buf is at least ossl_quic_vlint_decode_len(buf[0]) bytes in size
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* (unchecked)
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*/
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uint64_t ossl_quic_vlint_decode_unchecked(const unsigned char *buf);
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/*
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* Given a buffer buf of buf_len bytes in length, attempts to decode an encoded
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* QUIC variable-length integer at the start of the buffer and writes the result
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* to *v. If buf_len is inadequate, suggesting a truncated encoded integer, the
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* function fails and 0 is returned. Otherwise, returns the number of bytes
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* consumed.
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*
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* Precondition: buf is at least buf_len bytes in size
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* Precondition: v (unchecked)
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*/
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int ossl_quic_vlint_decode(const unsigned char *buf, size_t buf_len, uint64_t *v);
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# endif
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#endif
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