/*!
A documentation-only module for #\[deku\] attributes
# Scopes
To understand the `Scope` column of the table below:
```rust,ignore
#[deku(/* top-level */)]
struct DekuStruct {
#[deku( /* field */)]
field: u8,
}
#[deku(/* top-level */)]
enum DekuEnum {
#[deku(/* variant */)]
VariantA,
#[deku(/* variant */)]
VariantB( #[deku(/* field */)] u8 ),
#[deku(/* variant */)]
VariantC {
#[deku( /* field */)]
field: u8,
}
}
```
# List of attributes
| Attribute | Scope | Description
|-----------|------------------|------------
| [endian](#endian) | top-level, field | Set the endianness
| [magic](#magic) | top-level | A magic value that must be present at the start of this struct/enum
| [assert](#assert) | field | Assert a condition
| [assert_eq](#assert_eq) | field | Assert equals on the field
| [bits](#bits) | field | Set the bit-size of the field
| [bytes](#bytes) | field | Set the byte-size of the field
| [count](#count) | field | Set the field representing the element count of a container
| [bits_read](#bits_read) | field | Set the field representing the number of bits to read into a container
| [bytes_read](#bytes_read) | field | Set the field representing the number of bytes to read into a container
| [until](#until) | field | Set a predicate returning when to stop reading elements into a container
| [update](#update) | field | Apply code over the field when `.update()` is called
| [temp](#temp) | field | Read the field but exclude it from the struct/enum
| [skip](#skip) | field | Skip the reading/writing of a field
| [pad_bytes_before](#pad_bytes_before) | field | Skip bytes before reading, pad before writing
| [pad_bits_before](#pad_bits_before) | field | Skip bits before reading, pad before writing
| [pad_bytes_after](#pad_bytes_after) | field | Skip bytes after reading, pad after writing
| [pad_bits_after](#pad_bits_after) | field | Skip bits after reading, pad after writing
| [cond](#cond) | field | Conditional expression for the field
| [default](#default) | field | Provide default value. Used with [skip](#skip) or [cond](#cond)
| [map](#map) | field | Apply a function over the result of reading
| [reader](#readerwriter) | variant, field | Custom reader code
| [writer](#readerwriter) | variant, field | Custom writer code
| [ctx](#ctx) | top-level, field| Context list for context sensitive parsing
| [ctx_default](#ctx_default) | top-level, field| Default context values
| enum: [id](#id) | top-level, variant | enum or variant id value
| enum: [id_pat](#id_pat) | variant | variant id match pattern
| enum: [type](#type) | top-level | Set the type of the variant `id`
| enum: [bits](#bits-1) | top-level | Set the bit-size of the variant `id`
| enum: [bytes](#bytes-1) | top-level | Set the byte-size of the variant `id`
# endian
Set to read/write bytes in a specific byte order.
Values: `big`, `little` or an expression which returns a [`Endian`](super::ctx::Endian)
Precedence: field > top-level > system endianness (default)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
// #[deku(endian = "little")] // top-level, defaults to system endianness
struct DekuTest {
#[deku(endian = "big")] // field-level override
field_be: u16,
field_default: u16, // defaults to top-level
}
let data: Vec<u8> = vec![0xAB, 0xCD, 0xAB, 0xCD];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_be: 0xABCD,
field_default: 0xCDAB,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
**Note**: The `endian` is passed as a context argument to sub-types
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(endian = "endian", ctx = "endian: deku::ctx::Endian")] // context passed from `DekuTest` top-level endian
struct Child {
field_a: u16
}
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(endian = "little")] // top-level, defaults to system endianness
struct DekuTest {
#[deku(endian = "big")] // field-level override
field_be: u16,
field_default: u16, // defaults to top-level
// because a top-level endian is specified,
// it is passed as a context
field_child: Child,
}
let data: Vec<u8> = vec![0xAB, 0xCD, 0xAB, 0xCD, 0xEF, 0xBE];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_be: 0xABCD,
field_default: 0xCDAB,
field_child: Child { field_a: 0xBEEF }
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# magic
Sets a "magic" value that must be present in the data at the start of
a struct/enum when reading, and that is written out of the start of
that type's data when writing.
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(magic = b"deku")]
struct DekuTest {
data: u8
}
let data: Vec<u8> = vec![b'd', b'e', b'k', b'u', 50];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { data: 50 },
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# assert
Assert a condition after reading and before writing a field
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(assert = "*data >= 8")]
data: u8
}
let data: Vec<u8> = vec![0x00, 0x01, 0x02];
let value = DekuTest::try_from(data.as_ref());
assert_eq!(
Err(DekuError::Assertion("DekuTest.data field failed assertion: * data >= 8".into())),
value
);
```
# assert_eq
Assert equals after reading and before writing a field
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(assert_eq = "0x01")]
data: u8,
}
let data: Vec<u8> = vec![0x01];
let mut value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { data: 0x01 },
value
);
value.data = 0x02;
let value: Result<Vec<u8>, DekuError> = value.try_into();
assert_eq!(
Err(DekuError::Assertion("DekuTest.data field failed assertion: data == 0x01".into())),
value
);
```
# bits
Set the bit-size of the field
**Note**: Cannot be used in combination with [bytes](#bytes)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(bits = 2)]
field_a: u8,
#[deku(bits = 6)]
field_b: u8,
field_c: u8, // defaults to size_of<u8>*8
}
let data: Vec<u8> = vec![0b11_101010, 0xFF];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0b11,
field_b: 0b101010,
field_c: 0xFF,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# bytes
Set the byte-size of the field
**Note**: Cannot be used in combination with [bits](#bits)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(bytes = 2)]
field_a: u32,
field_b: u8, // defaults to size_of<u8>
}
let data: Vec<u8> = vec![0xAB, 0xCD, 0xFF];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0xCDAB,
field_b: 0xFF,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# count
Specify the field representing the length of the container, i.e. a Vec
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(update = "self.items.len()")]
count: u8,
#[deku(count = "count")]
items: Vec<u8>,
}
let data: Vec<u8> = vec![0x02, 0xAB, 0xCD];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
count: 0x02,
items: vec![0xAB, 0xCD],
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
**Note**: See [update](#update) for more information on the attribute!
# bytes_read
Specify the field representing the total number of bytes to read into a container
See the following example, where `InnerDekuTest` is 2 bytes, so setting `bytes_read` to
4 will read 2 items into the container:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct InnerDekuTest {
field_a: u8,
field_b: u8
}
# #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(update = "(self.items.len() / 2)")]
bytes: u8,
#[deku(bytes_read = "bytes")]
items: Vec<InnerDekuTest>,
}
let data: Vec<u8> = vec![0x04, 0xAB, 0xBC, 0xDE, 0xEF];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
bytes: 0x04,
items: vec![
InnerDekuTest{field_a: 0xAB, field_b: 0xBC},
InnerDekuTest{field_a: 0xDE, field_b: 0xEF}],
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
**Note**: See [update](#update) for more information on the attribute!
# bits_read
This is equivalent to [bytes_read](#bytes_read), however specifies the bit limit instead
of a byte limit
# until
Specifies a predicate which sets when to stop reading values into the container.
**Note**: The last value which matches the predicate is read
The predicate is given a borrow to each item as it is read, and must return a boolean
as to whether this should be the last item or not. If it returns true, then reading stops.
A good example of this is to read a null-terminated string:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# use std::ffi::CString;
# #[derive(Debug, PartialEq, DekuRead)]
struct DekuTest {
#[deku(until = "|v: &u8| *v == 0")]
string: Vec<u8>
}
let data: Vec<u8> = vec![b'H', b'e', b'l', b'l', b'o', 0];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
string: CString::new(b"Hello".to_vec()).unwrap().into_bytes_with_nul()
},
value
);
```
# update
Specify custom code to run on the field when `.update()` is called on the struct/enum
Example:
```rust
use deku::prelude::*;
use std::convert::{TryInto, TryFrom};
#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(update = "self.items.len()")]
count: u8,
#[deku(count = "count")]
items: Vec<u8>,
}
let data: Vec<u8> = vec![0x02, 0xAB, 0xCD];
// `mut` so it can be updated
let mut value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { count: 0x02, items: vec![0xAB, 0xCD] },
value
);
// push a new item to the vec
value.items.push(0xFF);
// update it, this will update the `count` field
value.update().unwrap();
assert_eq!(
DekuTest { count: 0x03, items: vec![0xAB, 0xCD, 0xFF] },
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x03, 0xAB, 0xCD, 0xFF], value);
```
# temp
A temporary field
Included in the reading of the struct/enum but not stored
**Note**: Struct/enum must be derived with `#[deku_derive(...)]` to derive
`DekuRead` and/or `DekuWrite`, not with `#[derive(...)]`. This is because the
struct/enum needs to be modified at compile time.
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[deku_derive(DekuRead, DekuWrite)]
#[derive(Debug, PartialEq)]
struct DekuTest {
#[deku(temp)]
num_items: u8,
#[deku(count = "num_items", endian = "big")]
items: Vec<u16>,
}
let data: Vec<u8> = vec![0x01, 0xBE, 0xEF];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
items: vec![0xBEEF]
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0xBE, 0xEF], value);
```
# skip
Skip the reading/writing of a field.
Defaults value to [default](#default)
**Note**: Can be paired with [cond](#cond) to have conditional skipping
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
field_a: u8,
#[deku(skip)]
field_b: Option<u8>,
field_c: u8,
}
let data: Vec<u8> = vec![0x01, 0x02];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { field_a: 0x01, field_b: None, field_c: 0x02 },
value
);
```
# pad_bytes_before
Skip a number of bytes before reading, pad with 0x00s before writing
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
pub struct DekuTest {
pub field_a: u8,
#[deku(pad_bytes_before = "2")]
pub field_b: u8,
}
let data: Vec<u8> = vec![0xAA, 0xBB, 0xCC, 0xDD];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0xAA,
field_b: 0xDD,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0xAA, 0x00, 0x00, 0xDD], value);
```
# pad_bits_before
Skip a number of bytes before reading, pad with 0s before writing
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(bits = 2)]
field_a: u8,
#[deku(pad_bits_before = "2", bits = 4)]
field_b: u8,
}
let data: Vec<u8> = vec![0b10_01_1001];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0b10,
field_b: 0b1001,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0b10_00_1001], value);
```
# pad_bytes_after
Skip a number of bytes after reading, pad with 0x00s after writing
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
pub struct DekuTest {
#[deku(pad_bytes_after = "2")]
pub field_a: u8,
pub field_b: u8,
}
let data: Vec<u8> = vec![0xAA, 0xBB, 0xCC, 0xDD];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0xAA,
field_b: 0xDD,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0xAA, 0x00, 0x00, 0xDD], value);
```
# pad_bits_after
Skip a number of bytes after reading, pad with 0s after writing
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(bits = 2, pad_bits_after = "2")]
field_a: u8,
#[deku(bits = 4)]
field_b: u8,
}
let data: Vec<u8> = vec![0b10_01_1001];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
field_a: 0b10,
field_b: 0b1001,
},
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0b10_00_1001], value);
```
# cond
Specify a condition to parse or skip a field
**Note**: Can be paired with [default](#default)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
field_a: u8,
#[deku(cond = "*field_a == 0x01")]
field_b: Option<u8>,
#[deku(cond = "*field_b == Some(0xFF)", default = "Some(0x05)")]
field_c: Option<u8>,
#[deku(skip, cond = "*field_a == 0x01", default = "Some(0x06)")]
field_d: Option<u8>,
}
let data: Vec<u8> = vec![0x01, 0x02];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { field_a: 0x01, field_b: Some(0x02), field_c: Some(0x05), field_d: Some(0x06)},
value
);
assert_eq!(
vec![0x01, 0x02, 0x05],
value.to_bytes().unwrap(),
)
```
# default
Default code tokens used with [skip](#skip) or [cond](#cond)
Defaults to `Default::default()`
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
field_a: u8,
#[deku(skip, default = "Some(*field_a)")]
field_b: Option<u8>,
field_c: u8,
}
let data: Vec<u8> = vec![0x01, 0x02];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { field_a: 0x01, field_b: Some(0x01), field_c: 0x02 },
value
);
```
# map
Specify a function or lambda to apply to the result of the read
Example:
Read a `u8` and apply a function to convert it to a `String`.
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead)]
struct DekuTest {
#[deku(map = "|field: u8| -> Result<_, DekuError> { Ok(field.to_string()) }")]
field_a: String,
#[deku(map = "DekuTest::map_field_b")]
field_b: String,
}
impl DekuTest {
fn map_field_b(field_b: u8) -> Result<String, DekuError> {
Ok(field_b.to_string())
}
}
let data: Vec<u8> = vec![0x01, 0x02];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { field_a: "1".to_string(), field_b: "2".to_string() },
value
);
```
# reader/writer
Specify custom reader or writer tokens for reading a field or variant
Example:
```rust
use std::convert::{TryInto, TryFrom};
use deku::bitvec::{BitSlice, BitVec, Msb0};
use deku::prelude::*;
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
#[deku(
reader = "DekuTest::read(deku::rest)",
writer = "DekuTest::write(deku::output, &self.field_a)"
)]
field_a: String,
}
impl DekuTest {
/// Read and convert to String
fn read(
rest: &BitSlice<Msb0, u8>,
) -> Result<(&BitSlice<Msb0, u8>, String), DekuError> {
let (rest, value) = u8::read(rest, ())?;
Ok((rest, value.to_string()))
}
/// Parse from String to u8 and write
fn write(output: &mut BitVec<Msb0, u8>, field_a: &str) -> Result<(), DekuError> {
let value = field_a.parse::<u8>().unwrap();
value.write(output, ())
}
}
let data: Vec<u8> = vec![0x01];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest { field_a: "1".to_string() },
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# ctx
This attribute allows sending and receiving context (variables/values) to sub-parsers/writers
**Note**: `endian`, `bytes`, `bits`, `count` attributes use `ctx` internally, see examples below
**top-level**: The value of a ctx attribute is a function argument list,
for example `#[deku(ctx = "a: u8, b: String")]`
**field-level**: The value of the ctx attribute is a list of expressions,
for example `#[deku("a, b")]`
**Visibility**: The following can be accessed:
1. All former fields which have been parsed (given as a reference).
2. `endian`, `bytes`, `bits` attributes declared on the top-level
- These are prepended to the list of ctx variables
Example
```rust
# use deku::prelude::*;
#[derive(DekuRead, DekuWrite)]
#[deku(ctx = "a: u8")]
struct Subtype {
#[deku(map = "|b: u8| -> Result<_, DekuError> { Ok(b + a) }")]
b: u8
}
#[derive(DekuRead, DekuWrite)]
struct Test {
a: u8,
#[deku(ctx = "*a")] // pass `a` to `SubType`, `a` is a reference
sub: Subtype
}
let data: Vec<u8> = vec![0x01, 0x02];
let (rest, value) = Test::from_bytes((&data[..], 0)).unwrap();
assert_eq!(value.a, 0x01);
assert_eq!(value.sub.b, 0x01 + 0x02)
```
**Note**: In addition, `endian`, `bytes` and `bits` use the `ctx` concept internally, examples below are equivalent:
Example:
```ignore
struct Type1 {
#[deku(endian = "big", bits = "1")]
field: u8,
}
// is equivalent to
struct Type1 {
#[deku(ctx = "Endian::Big, Size::Bits(1)")]
field: u8,
}
```
Example: Adding context
```ignore
#[deku(endian = "big")]
struct Type1 {
field_a: u16,
#[deku(bits = "5", ctx = "*field_a")]
field_b: SubType,
}
// is equivalent to
struct Type1 {
#[deku(ctx = "Endian::Big")]
field_a: u16,
#[deku(ctx = "Endian::Big, Size::Bits(5), *field_a")] // endian is prepended
field_b: SubType,
}
```
# ctx_default
When paired with the [`ctx`](#ctx) attribute, `ctx_default` provides default
values for the context
Example:
```rust
# use deku::prelude::*;
#[derive(DekuRead, DekuWrite)]
#[deku(ctx = "a: u8", ctx_default = "1")] // Defaults `a` to 1
struct Subtype {
#[deku(map = "|b: u8| -> Result<_, DekuError> { Ok(b + a) }")]
b: u8
}
#[derive(DekuRead, DekuWrite)]
struct Test {
a: u8,
#[deku(ctx = "*a")] // pass `a` to `SubType`, `a` is a reference
sub: Subtype
}
let data: Vec<u8> = vec![0x01, 0x02];
// Use with context from `Test`
let (rest, value) = Test::from_bytes((&data[..], 0)).unwrap();
assert_eq!(value.a, 0x01);
assert_eq!(value.sub.b, 0x01 + 0x02);
// Use as a stand-alone container, using defaults
// Note: `from_bytes` is now available on `SubType`
let data: Vec<u8> = vec![0x02];
let (rest, value) = Subtype::from_bytes((&data[..], 0)).unwrap();
assert_eq!(value.b, 0x01 + 0x02)
```
# id
## id (top-level)
Specify the enum id
This is useful in cases when the enum `id` is already consumed or is given externally
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
struct DekuTest {
my_id: u8,
data: u8,
#[deku(ctx = "*my_id")]
enum_from_id: MyEnum,
}
#[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(ctx = "my_id: u8", id = "my_id")]
enum MyEnum {
#[deku(id = "1")]
VariantA(u8),
#[deku(id = "2")]
VariantB,
}
let data: Vec<u8> = vec![0x01_u8, 0xff, 0xab];
let ret_read = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest {
my_id: 0x01,
data: 0xff,
enum_from_id: MyEnum::VariantA(0xab),
},
ret_read
);
let ret_write: Vec<u8> = ret_read.try_into().unwrap();
assert_eq!(ret_write, data)
```
## id (variant)
Specify the identifier of the enum variant, must be paired with [type](#type)
or [id (top-level)](#id-top-level)
**Note**:
- If no `id` is specified, it is defaulted to the discriminant value.
- The discriminant value is retreived using the `as` keyword.
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(type = "u8")]
enum DekuTest {
#[deku(id = "0x01")]
VariantA(u8),
#[deku(id = "0x02")]
VariantB(u8, u16),
}
let data: Vec<u8> = vec![0x01, 0xFF, 0x02, 0xAB, 0xEF, 0xBE];
let (rest, value) = DekuTest::from_bytes((data.as_ref(), 0)).unwrap();
assert_eq!(
DekuTest::VariantA(0xFF),
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x01, 0xFF], variant_bytes);
let (rest, value) = DekuTest::from_bytes(rest).unwrap();
assert_eq!(
DekuTest::VariantB(0xAB, 0xBEEF),
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x02, 0xAB, 0xEF, 0xBE], variant_bytes);
```
Example discriminant
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(type = "u8")]
enum DekuTest {
VariantA = 0x01,
VariantB,
}
let data: Vec<u8> = vec![0x01, 0x02];
let (rest, value) = DekuTest::from_bytes((data.as_ref(), 0)).unwrap();
assert_eq!(
DekuTest::VariantA,
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x01], variant_bytes);
let (rest, value) = DekuTest::from_bytes(rest).unwrap();
assert_eq!(
DekuTest::VariantB,
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x02], variant_bytes);
```
# id_pat
Specify the identifier in the form of a match pattern for the enum variant.
The enum variant must have space to store the identifier for proper writing.
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(type = "u8")]
enum DekuTest {
#[deku(id = "0x01")]
VariantA(u8),
#[deku(id_pat = "0x02..=0x06")]
VariantB {
id: u8
},
#[deku(id_pat = "_")]
VariantC(u8),
}
let data: Vec<u8> = vec![0x03, 0xFF];
let (rest, value) = DekuTest::from_bytes((data.as_ref(), 0)).unwrap();
assert_eq!(
DekuTest::VariantB { id: 0x03 },
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0x03], variant_bytes);
let (rest, value) = DekuTest::from_bytes(rest).unwrap();
assert_eq!(
DekuTest::VariantC(0xFF),
value
);
let variant_bytes: Vec<u8> = value.try_into().unwrap();
assert_eq!(vec![0xFF], variant_bytes);
```
# type
Specify the type of the enum variant id to consume, see [example](#id-variant)
# bits
Set the bit size of the enum variant `id`
**Note**: Cannot be used in combination with [bytes](#bytes)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(type = "u8", bits = "4")]
enum DekuTest {
#[deku(id = "0b1001")]
VariantA( #[deku(bits = "4")] u8, u8),
}
let data: Vec<u8> = vec![0b1001_0110, 0xFF];
let (rest, value) = DekuTest::from_bytes((&data, 0)).unwrap();
assert_eq!(
DekuTest::VariantA(0b0110, 0xFF),
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
# bytes
Set the byte size of the enum variant `id`
**Note**: Cannot be used in combination with [bits](#bits)
Example:
```rust
# use deku::prelude::*;
# use std::convert::{TryInto, TryFrom};
# #[derive(PartialEq, Debug, DekuRead, DekuWrite)]
#[deku(type = "u32", bytes = "2")]
enum DekuTest {
#[deku(id = "0xBEEF")]
VariantA(u8),
}
let data: Vec<u8> = vec![0xEF, 0xBE, 0xFF];
let value = DekuTest::try_from(data.as_ref()).unwrap();
assert_eq!(
DekuTest::VariantA(0xFF),
value
);
let value: Vec<u8> = value.try_into().unwrap();
assert_eq!(data, value);
```
*/