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Possibly useful `read` and `write` functions for `buffer`s that aren't inluded in the normal API
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| --[[ | |
| Copyright 2024 Arvid | |
| Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: | |
| The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. | |
| THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | |
| ]] | |
| -- Possibly useful `read` and `write` functions for `buffer`s that aren't inluded in the normal API | |
| local function writef16(b: buffer, offset: number, value: number) | |
| if value > 65504 then | |
| buffer.writeu16(b, offset, 0b0_11111_0000000000) | |
| elseif value < -65504 then | |
| buffer.writeu16(b, offset, 0b1_11111_0000000000) | |
| elseif value ~= value then | |
| buffer.writeu16(b, offset, 0b1_11111_0000000001) | |
| elseif value == 0 then | |
| buffer.writeu16(b, offset, 0) | |
| else | |
| local absValue = math.abs(value) | |
| local interval = math.ldexp(1, math.floor(math.log(absValue, 2)) - 10) | |
| local roundedValue = math.floor(absValue / interval) * interval | |
| local fraction, unbiasedExponent = math.frexp(roundedValue) | |
| local exponent = unbiasedExponent + 14 | |
| -- stylua: ignore start | |
| local mantissa = math.round(if exponent <= 0 | |
| then fraction * 0x400 / math.ldexp(1, math.abs(exponent)) | |
| else fraction * 0x800) % 0x400 | |
| buffer.writeu16(b, offset, mantissa | |
| + math.max(exponent, 0) * 0x400 | |
| + if value < 0 then 0x8000 else 0) | |
| -- stylua: ignore end | |
| end | |
| end | |
| local function readf16(b: buffer, offset: number): number | |
| local uintForm = buffer.readu16(b, offset) | |
| local mantissa_exponent = uintForm % 0x8000 | |
| if mantissa_exponent == 0b11111_0000000000 then | |
| return if uintForm // 0x8000 == 1 then -math.huge else math.huge | |
| elseif mantissa_exponent == 0b11111_0000000001 then | |
| return 0 / 0 | |
| elseif mantissa_exponent == 0b00000_0000000000 then | |
| return 0 | |
| else | |
| local mantissa = mantissa_exponent % 0x400 | |
| local exponent = mantissa_exponent // 0x400 | |
| -- stylua: ignore | |
| local fraction = if exponent == 0 | |
| then mantissa / 0x400 | |
| else mantissa / 0x800 + 0.5 | |
| local value = math.ldexp(fraction, exponent - 14) | |
| return if uintForm // 0x8000 == 1 then -value else value | |
| end | |
| end | |
| local function writeu24(b: buffer, offset: number, value: number) | |
| buffer.writeu8(b, offset, value) | |
| buffer.writeu16(b, offset + 1, value // 0x100) | |
| end | |
| local function readu24(b: buffer, offset: number): number | |
| return buffer.readu8(b, offset) + buffer.readu16(b, offset + 1) * 0x100 | |
| end | |
| local function writei24(b: buffer, offset: number, value: number) | |
| local uint = (value + 0x1000000) % 0x1000000 | |
| buffer.writeu8(b, offset, uint) | |
| buffer.writeu16(b, offset + 1, uint // 0x100) | |
| end | |
| local function readi24(b: buffer, offset: number): number | |
| local uint = buffer.readu8(b, offset) + buffer.readu16(b, offset + 1) * 0x100 | |
| return (uint + 0x800000) % 0x1000000 - 0x800000 | |
| end | |
| local function writeu48(b: buffer, offset: number, value: number) | |
| buffer.writeu32(b, offset, value) | |
| buffer.writeu16(b, offset + 4, value // 0x100000000) | |
| end | |
| local function readu48(b: buffer, offset: number): number | |
| return buffer.readu32(b, offset) + buffer.readu16(b, offset + 4) * 0x100000000 | |
| end | |
| local function writei48(b: buffer, offset: number, value: number) | |
| local uint = (value + 0x1000000000000) % 0x1000000000000 | |
| buffer.writeu32(b, offset, uint) | |
| buffer.writeu16(b, offset + 4, uint // 0x100000000) | |
| end | |
| local function readi48(b: buffer, offset: number): number | |
| local uint = buffer.readu32(b, offset) + buffer.readu16(b, offset + 4) * 0x100000000 | |
| return (uint + 0x800000000000) % 0x1000000000000 - 0x800000000000 | |
| end |
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