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v/vlib/encoding/base58/base58.v

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// algorthim is adapted from https://github.com/mr-tron/base58 under the MIT license
module base58
import math
// encode_int encodes any integer type to base58 string with Bitcoin alphabet
pub fn encode_int(input int) !string {
return encode_int_walpha(input, btc_alphabet)
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}
// encode_int_walpha any integer type to base58 string with custom alphabet
pub fn encode_int_walpha(input int, alphabet Alphabet) !string {
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if input <= 0 {
return error(@MOD + '.' + @FN + ': input must be greater than zero')
}
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mut buffer := []u8{}
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mut i := input
for i > 0 {
remainder := i % 58
buffer << alphabet.encode[i8(remainder)]
// This needs to be casted so byte inputs can
// be used. i8 because remainder will never be
// over 58.
i = i / 58
}
return buffer.reverse().bytestr()
}
// encode encodes the input string to base58 with the Bitcoin alphabet
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pub fn encode(input string) string {
return encode_walpha(input, btc_alphabet)
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}
// encode_bytes encodes the input array to base58, with the Bitcoin alphabet
pub fn encode_bytes(input []u8) []u8 {
return encode_walpha_bytes(input, btc_alphabet)
}
// encode_walpha encodes the input string to base58 with a custom aplhabet
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pub fn encode_walpha(input string, alphabet Alphabet) string {
if input.len == 0 {
return ''
}
bin := input.bytes()
return encode_walpha_bytes(bin, alphabet).bytestr()
}
// encode_walpha encodes the input array to base58 with a custom aplhabet
pub fn encode_walpha_bytes(input []u8, alphabet Alphabet) []u8 {
if input.len == 0 {
return []
}
mut sz := input.len
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mut zcount := 0
for zcount < sz && input[zcount] == 0 {
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zcount++
}
// It is crucial to make this as short as possible, especially for
// the usual case of Bitcoin addresses
sz = zcount + (sz - zcount) * 555 / 406 + 1
// integer simplification of
// ceil(log(256)/log(58))
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mut out := []u8{len: sz}
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mut i := 0
mut high := 0
mut carry := u32(0)
high = sz - 1
for b in input {
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i = sz - 1
for carry = u32(b); i > high || carry != 0; i-- {
carry = carry + 256 * u32(out[i])
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out[i] = u8(carry % 58)
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carry /= 58
}
high = 1
}
// determine additional "zero-gap" in the buffer, aside from zcount
for i = zcount; i < sz && out[i] == 0; i++ {}
// now encode the values with actual alphabet in-place
val := out[i - zcount..]
sz = val.len
for i = 0; i < sz; i++ {
out[i] = alphabet.encode[val[i]]
}
return out[..sz]
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}
// decode_int decodes base58 string to an integer with Bitcoin alphabet
pub fn decode_int(input string) !int {
return decode_int_walpha(input, btc_alphabet)
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}
// decode_int_walpha decodes base58 string to an integer with custom alphabet
pub fn decode_int_walpha(input string, alphabet Alphabet) !int {
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mut total := 0 // to hold the results
b58 := input.reverse()
for i, ch in b58 {
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ch_i := alphabet.encode.bytestr().index_u8(ch)
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if ch_i == -1 {
return error(@MOD + '.' + @FN +
': input string contains values not found in the provided alphabet')
}
val := ch_i * math.pow(58, i)
total += int(val)
}
return total
}
// decode decodes the base58 input string, using the Bitcoin alphabet
pub fn decode(str string) !string {
return decode_walpha(str, btc_alphabet)
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}
// decode_bytes decodes the base58 encoded input array, using the Bitcoin alphabet
pub fn decode_bytes(input []u8) ![]u8 {
return decode_walpha_bytes(input, btc_alphabet)
}
// decode_walpha decodes the base58 encoded input string, using custom alphabet
pub fn decode_walpha(input string, alphabet Alphabet) !string {
if input.len == 0 {
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return ''
}
bin := input.bytes()
res := decode_walpha_bytes(bin, alphabet)!
return res.bytestr()
}
// decode_walpha_bytes decodes the base58 encoded input array using a custom alphabet
pub fn decode_walpha_bytes(input []u8, alphabet Alphabet) ![]u8 {
if input.len == 0 {
return []
}
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zero := alphabet.encode[0]
b58sz := input.len
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mut zcount := 0
for i := 0; i < b58sz && input[i] == zero; i++ {
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zcount++
}
mut t := u64(0)
mut c := u64(0)
// the 32-bit algorithm stretches the result up to 2x
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mut binu := []u8{len: 2 * ((b58sz * 406 / 555) + 1)}
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mut outi := []u32{len: (b58sz + 3) / 4}
for _, r in input {
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if r > 127 {
panic(@MOD + '.' + @FN +
': high-bit set on invalid digit; outside of ascii range ($r). This should never happen.')
}
if alphabet.decode[r] == -1 {
return error(@MOD + '.' + @FN + ': invalid base58 digit ($r)')
}
c = u64(alphabet.decode[r])
for j := outi.len - 1; j >= 0; j-- {
t = u64(outi[j]) * 58 + c
c = t >> 32
outi[j] = u32(t & 0xffffffff)
}
}
// initial mask depend on b58sz, on further loops it always starts at 24 bits
mut mask := (u32(b58sz % 4) * 8)
if mask == 0 {
mask = 32
}
mask -= 8
mut out_len := 0
for j := 0; j < outi.len; j++ {
for mask < 32 {
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binu[out_len] = u8(outi[j] >> mask)
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mask -= 8
out_len++
}
mask = 24
}
// find the most significant byte post-decode, if any
for msb := zcount; msb < binu.len; msb++ { // loop relies on u32 overflow
if binu[msb] > 0 {
return binu[msb - zcount..out_len]
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}
}
// it's all zeroes
return binu[..out_len]
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}