146 lines
3.3 KiB
Markdown
146 lines
3.3 KiB
Markdown
---
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id: bytes-reference
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title: Bytes — Manipulate bytes data
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---
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import Syntax from '@theme/Syntax';
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## Bytes.concat(b1: bytes, b2: bytes) : bytes
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Concatenate together two `bytes` arguments and return the result.
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<Syntax syntax="pascaligo">
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```pascaligo
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function concat_op (const s : bytes) : bytes is
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begin skip end with bytes_concat(s , 0x7070)
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```
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</Syntax>
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<Syntax syntax="cameligo">
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```cameligo
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let concat_op (s : bytes) : bytes =
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Bytes.concat s 0x7070
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```
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</Syntax>
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<Syntax syntax="reasonligo">
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```reasonligo
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let concat_op = (s: bytes): bytes => Bytes.concat(s, 0x7070);
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```
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</Syntax>
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## Bytes.slice(pos1: nat, pos2: nat, data: bytes) : bytes
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Extract the bytes between `pos1` and `pos2`. **Positions are zero indexed and
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inclusive**. For example if you gave the input "ff7a7aff" to the following:
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<Syntax syntax="pascaligo">
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```pascaligo
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function slice_op (const s : bytes) : bytes is
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begin skip end with bytes_slice(1n , 2n , s)
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```
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</Syntax>
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<Syntax syntax="cameligo">
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```cameligo
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let slice_op (s : bytes) : bytes =
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Bytes.slice 1n 2n s
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```
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</Syntax>
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<Syntax syntax="reasonligo">
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```
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let slice_op = (s: bytes): bytes => Bytes.slice(1n, 2n, s);
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```
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</Syntax>
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It would return "7a7a" rather than "ff7a" or "ff" or "7a".
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## Bytes.pack(data: a') : bytes
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Converts Michelson data structures to a binary format for serialization.
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> ⚠️ `PACK` and `UNPACK` are features of Michelson that are intended to be used by people that really know what they're doing. There are several failure cases (such as `UNPACK`ing a lambda from an untrusted source), most of which are beyond the scope of this document. Don't use these functions without doing your homework first.
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<Syntax syntax="pascaligo">
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```pascaligo
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function id_string (const p : string) : option(string) is block {
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const packed : bytes = bytes_pack(p) ;
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} with (bytes_unpack(packed): option(string))
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```
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</Syntax>
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<Syntax syntax="cameligo">
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```cameligo
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let id_string (p: string) : string option =
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let packed: bytes = Bytes.pack p in
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((Bytes.unpack packed): string option)
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```
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</Syntax>
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<Syntax syntax="reasonligo">
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```reasonligo
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let id_string = (p: string) : option(string) => {
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let packed : bytes = Bytes.pack(p);
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((Bytes.unpack(packed)): option(string));
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};
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```
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</Syntax>
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## Bytes.unpack(packed: bytes) : a'
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Reverses the result of using `unpack` on data, going from Michelson's binary
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serialization format to the `option` type annotated on the call.
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> ⚠️ `PACK` and `UNPACK` are features of Michelson that are intended to be used by people that really know what they're doing. There are several failure cases (such as `UNPACK`ing a lambda from an untrusted source), most of which are beyond the scope of this document. Don't use these functions without doing your homework first.
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<Syntax syntax="pascaligo">
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```pascaligo
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function id_string (const p : string) : option(string) is block {
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const packed : bytes = bytes_pack(p) ;
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} with (bytes_unpack(packed): option(string))
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```
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</Syntax>
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<Syntax syntax="cameligo">
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```cameligo
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let id_string (p: string) : string option =
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let packed: bytes = Bytes.pack p in
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((Bytes.unpack packed): string option)
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```
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</Syntax>
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<Syntax syntax="reasonligo">
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```reasonligo
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let id_string = (p: string) : option(string) => {
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let packed : bytes = Bytes.pack(p);
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((Bytes.unpack(packed)): option(string));
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};
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```
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</Syntax>
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