Lib.rs

关联值可以直接实例化，然后生成原始数据。

use alsa_ctl_tlv_codec::DbScale;

let scale = DbScale{
    min: -100,
    step: 10,
    mute_avail: true,
};

let raw_generated: Vec<u32> = (&scale).into();

let raw_expected = [1 as u32, 8, -100i32 as u32, 10 | 0x00010000];

assert_eq!(&raw_generated[..], &raw_expected[..]);

一些关联值是容器类型，它聚集了其他项。在这种情况下，使用 TlvItem 对 Container 进行聚合。

use alsa_ctl_tlv_codec::*;

let cntr = Container{
    entries: vec![
        TlvItem::Chmap(Chmap{
            mode: ChmapMode::Fixed,
            entries: vec![
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontLeft), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontRight), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::LowFrequencyEffect), ..Default::default()},
            ],
        }),
        TlvItem::Chmap(Chmap{
            mode: ChmapMode::ArbitraryExchangeable,
            entries: vec![
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontLeft), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontRight), ..Default::default()},
            ],
        }),
        TlvItem::Chmap(Chmap{
            mode: ChmapMode::PairedExchangeable,
            entries: vec![
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontLeft), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::FrontRight), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::RearLeft), ..Default::default()},
                ChmapEntry{pos: ChmapPos::Generic(ChmapGenericPos::RearRight), ..Default::default()},
            ],
        }),
    ],
};

let raw_generated: Vec<u32> = (&cntr).into();

let raw_expected = [0 as u32, 60,
                    0x101, 12, 3, 4, 8,
                    0x102, 8, 3, 4,
                    0x103, 16, 3, 4, 5, 6];

assert_eq!(&raw_generated[..], &raw_expected[..]);

工具

一些程序位于 src/bin 目录下。

tlv-decode.rs

此程序从 stdin 解码 TLV 的原始数据，或作为命令行参数的数值字面量，然后打印解析的结构。

如果没有命令行参数，它将打印帮助信息并退出。

$ cargo run --bin tlv-decode
Usage:
  tlv-decode MODE DATA | "-"

  where:
    MODE:           The mode to process after parsing DATA:
                        "structure":    prints data structures.
                        "macro":        prints C macro expression
                        "literal":      prints space-separated decimal array.
                        "raw":          prints binary with host endian.
    DATA:           space-separated DECIMAL and HEXADECIMAL array for the data of TLV.
    "-":            use binary from STDIN to interpret DATA according to host endian.
    DECIMAL:        decimal number. It can be signed if needed.
    HEXADECIMAL:    hexadecimal number. It should have '0x' as prefix.

对于命令行参数中的 TLV 数据

$ cargo run --bin tlv-decode -- structure 5 8 0xfffffe00 128
...
DbInterval(DbInterval { min: -512, max: 128, linear: false, mute_avail: true })

对于来自 STDIN 的 TLV 数据，在机器架构为小端的情况下

$ echo -en "\x05\x00\x00\x00\x08\x00\x00\x00\x00\xfe\xff\xff\x80\x00\x00\x00" | \
    cargo run --bin tlv-decode -- structure -
...
DbInterval(DbInterval { min: -512, max: 128, linear: false, mute_avail: true })

TLV 数据可以以 C 语言宏表达式形式打印

$ echo -en "\x05\x00\x00\x00\x08\x00\x00\x00\x00\xfe\xff\xff\x80\x00\x00\x00" | \
    cargo run --bin tlv-decode -- macro -
...
SNDRV_CTL_TLVD_ITEM ( SNDRV_CTL_TLVT_DB_MINMAX_MUTE, 0xfffffe00, 0x80 ) 

TLV 数据可以以 u32 数值字面量数组或按主机端序对齐的 u8 二进制形式打印

$ echo -en "\x05\x00\x00\x00\x08\x00\x00\x00\x00\xfe\xff\xff\x80\x00\x00\x00" | \
    cargo run --bin tlv-decode -- literal -
...
5 8 4294966784 128 

$ echo -en "\x05\x00\x00\x00\x08\x00\x00\x00\x00\xfe\xff\xff\x80\x00\x00\x00" | \
    cargo run --bin tlv-decode -- raw -
...

db-calculate.rs

此程序根据 STDIN 或命令行参数中的 TLV 数据，计算控制元素的 dB 值和原始值。它使用双精度浮点数进行 dB 计算。对于线性类型的 dB 计算，它使用指数和对数。

如果没有命令行参数，它将打印帮助信息并退出。

$ cargo run --bin db-calculate
Usage:
  db-calculate "db" DECIMAL-FLOATING-POINT VALUE-RANGE DATA | "-"
  db-calculate "value" DECIMAL | HEXADECIMAL VALUE-RANGE DATA | "-"

  where:
    "db":                   Use this program for db calculation.
    "value":                Use this program for value calculation.
    DECIMAL-FLOATING-POINT: decimal floating point number. It can be signed if needed.
    DECIMAL:                decimal number. It can be signed if needed.
    HEXADECIMAL:            hexadecimal number. It should have '0x' as prefix.
    VALUE-RANGE:            space-separated triplet of MIN, MAX, and STEP comes from information of
                            control element. All of them are DECIMAL or HEXADECIMAL.
    DATA:                   space-separated DECIMAL and HEXADECIMAL array for the data of TLV.
    "-":                    use STDIN to interpret DATA according to host endian.

   When data of TLV has information to support mute, "-9999999" for value and "-inf" for db are
   available.

对于基于 STDIN 的 TLV 数据从 dB 到值的计算，在机器架构为小端的情况下

$ echo -en "\x05\x00\x00\x00\x08\x00\x00\x00\x00\xfe\xff\xff\x80\x00\x00\x00" | \
    cargo run --bin db-calculate db 1.0    128 512 1    -
  ...
  495

对于基于命令行参数的 TLV 数据从值到 dB 的计算

$ cargo run --bin db-calculate value 495    128 512 1    5 8 0xfffffe00 0
  ...
  0.996666666666667

计算没有经过验证的数字。

许可证

alsa-ctl-tlv-codec crate 在 MIT 许可证 下发布。

支持

如果发现问题，请在 https://github.com/alsa-project/snd-firewire-ctl-services/ 中提交。