package core:encoding/varint
Source

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    Overview

    Implementation of the LEB128 variable integer encoding as used by DWARF encoding and DEX files, among others.

    Author of this Odin package: Jeroen van Rijn

    Example: 
    package main

import "core:encoding/varint"
import "core:fmt"

main :: proc() {
	buf: [varint.LEB128_MAX_BYTES]u8

	value := u128(42)

	encode_size, encode_err := varint.encode_uleb128(buf[:], value)
	assert(encode_size == 1 && encode_err == .None)

	fmt.printf("Encoded as %v\n", buf[:encode_size])
	decoded_val, decode_size, decode_err := varint.decode_uleb128(buf[:])

	assert(decoded_val == value && decode_size == encode_size && decode_err == .None)
	fmt.printf("Decoded as %v, using %v byte%v\n", decoded_val, decode_size, "" if decode_size == 1 else "s")
}

Copyright 2022 Jeroen van Rijn <nom@duclavier.com>.
Made available under Odin's BSD-3 license.

List of contributors:
	Jeroen van Rijn: Initial implementation.

    Index

    Types (1)
    Constants (1)
    Variables (0)

    This section is empty.

    Procedure Groups (2)

    Types

    Error ¶
    Source

    Error :: enum int {
	None             = 0, 
	Buffer_Too_Small = 1, 
	Value_Too_Large  = 2, 
}
    Related Procedures With Returns

    Constants

    LEB128_MAX_BYTES ¶
    Source

    LEB128_MAX_BYTES :: 19
     

    In theory we should use the bigint package. In practice, varints bigger than this indicate a corrupted file. Instead we'll set limits on the values we'll encode/decode 18 * 7 bits = 126, which means that a possible 19th byte may at most be 0b0000_0011.

    Variables

    This section is empty.

    Procedures

    decode_ileb128_buffer ¶
    Source

    decode_ileb128_buffer :: proc(buf: []u8) -> (val: i128, size: int, err: Error) {…}
     

    Decode a slice of bytes encoding a signed LEB128 integer into value and number of bytes used. Returns size == 0 for an invalid value, empty slice, or a varint > 18 bytes.

    decode_ileb128_byte ¶
    Source

    decode_ileb128_byte :: proc(input: u8, offset: int, accumulator: i128) -> (val: i128, size: int, err: Error) {…}
     

    Decode a a signed LEB128 integer into value and number of bytes used, one byte at a time. Returns size == 0 for an invalid value, empty slice, or a varint > 18 bytes.

    decode_uleb128_buffer ¶
    Source

    decode_uleb128_buffer :: proc(buf: []u8) -> (val: u128, size: int, err: Error) {…}
     

    Decode a slice of bytes encoding an unsigned LEB128 integer into value and number of bytes used. Returns size == 0 for an invalid value, empty slice, or a varint > 18 bytes.

    decode_uleb128_byte ¶
    Source

    decode_uleb128_byte :: proc(input: u8, offset: int, accumulator: u128) -> (val: u128, size: int, err: Error) {…}
     

    Decodes an unsigned LEB128 integer into value a byte at a time. Returns .None when decoded properly, .Value_Too_Large when they value exceeds the limits of a u128, and .Buffer_Too_Small when it's not yet fully decoded.

    encode_ileb128 ¶
    Source

    encode_ileb128 :: proc(buf: []u8, val: i128) -> (size: int, err: Error) {…}
     

    Encode val into buf as a signed LEB128 encoded series of bytes. buf must be appropriately sized.

    encode_uleb128 ¶
    Source

    encode_uleb128 :: proc(buf: []u8, val: u128) -> (size: int, err: Error) {…}
     

    Encode val into buf as an unsigned LEB128 encoded series of bytes. buf must be appropriately sized.

    Procedure Groups

    decode_ileb128 ¶
    Source

    decode_ileb128 :: proc{
	decode_ileb128_buffer,
	decode_ileb128_byte,
}

    decode_uleb128 ¶
    Source

    decode_uleb128 :: proc{
	decode_uleb128_buffer,
	decode_uleb128_byte,
}

    Source Files

    Generation Information

    Generated with odin version dev-2024-12 (vendor "odin") Windows_amd64 @ 2024-12-17 21:11:00.973707700 +0000 UTC