fastalp 0.1.22

use std::mem::size_of;

/// Bits per byte constant.
/// 每字节比特数常量
pub const BITS_PER_BYTE: usize = 8;

/// Bits in u64 constant.
/// u64 比特数常量
pub const BITS_U64: usize = 64;

/// Byte size of u16.
/// u16 字节大小
pub const BYTES_U16: usize = size_of::<u16>();

/// Byte size of u32.
/// u32 字节大小
pub const BYTES_U32: usize = size_of::<u32>();

/// Byte size of u64.
/// u64 字节大小
pub const BYTES_U64: usize = size_of::<u64>();

/// Format type identifier for f64 ALP compressed chunk.
/// f64 ALP 压缩数据块类型标识
pub const TYPE_F64: u8 = 1;

/// Format type identifier for f32 ALP compressed chunk.
/// f32 ALP 压缩数据块类型标识
pub const TYPE_F32: u8 = 2;

/// Format type identifier for f64 raw uncompressed fallback chunk.
/// f64 未压缩原始保底回退数据块类型标识
pub const TYPE_F64_RAW: u8 = 3;

/// Format type identifier for f32 raw uncompressed fallback chunk.
/// f32 未压缩原始保底回退数据块类型标识
pub const TYPE_F32_RAW: u8 = 4;

/// Maximum decimal exponent for double precision f64.
/// f64 最大十进制指数
pub const MAX_EXPONENT_F64: u8 = 18;

/// Maximum decimal exponent for single precision f32.
/// f32 最大十进制指数
pub const MAX_EXPONENT_F32: u8 = 10;

/// Maximum factor exponent for f64.
/// f64 最大因子指数
pub const MAX_FAC_F64: u8 = 8;

/// Maximum factor exponent for f32.
/// f32 最大因子指数
pub const MAX_FAC_F32: u8 = 4;

/// Magic rounding number for fast double precision float-to-int conversion (1.5 * 2^52).
/// f64 快速舍入整型魔数 (1.5 * 2^52)
pub const MAGIC_NUMBER_F64: f64 = 6755399441055744.0;

/// Magic rounding number for fast single precision float-to-int conversion (1.5 * 2^23).
/// f32 快速舍入整型魔数 (1.5 * 2^23)
pub const MAGIC_NUMBER_F32: f32 = 12582912.0;

/// Maximum encodable finite threshold for f64.
/// f64 编码上限阈值
pub const ENCODING_UPPER_LIMIT_F64: f64 = 9223372036854774784.0;

/// Maximum encodable finite threshold for f32.
/// f32 编码上限阈值
pub const ENCODING_UPPER_LIMIT_F32: f32 = 2147483520.0;

/// Minimum header length in bytes for empty sequences or raw fallback mode.
/// 最小头部长度 (字节): 仅空序列 count == 0 或 raw 回退模式时使用 (1B 类型 + 2B 数量)
pub const MIN_HEADER_LEN: usize = 3;

/// Full header length in bytes (1B type + 2B count + 2B packed parameters).
/// 完整头部长度 (字节): 1B 类型 + 2B 数量 + 2B 打包参数 (exp:5b, fac:4b, bit_width:7b)
pub const HEADER_LEN: usize = 5;

/// Header type byte index offset.
/// 头部类型字节偏移索引
pub const HDR_TYPE_IDX: usize = 0;

/// Header count start byte index.
/// 头部数量起始字节索引
pub const HDR_COUNT_START: usize = 1;

/// Header count end byte index.
/// 头部数量结束字节索引
pub const HDR_COUNT_END: usize = 3;

/// Header params start byte index.
/// 头部参数起始字节索引
pub const HDR_PARAMS_START: usize = 3;

/// Header params end byte index.
/// 头部参数结束字节索引
pub const HDR_PARAMS_END: usize = 5;

/// Exception count field length in bytes (u16).
/// 异常总数字段长度 (字节, u16)
pub const EXC_COUNT_LEN: usize = size_of::<u16>();

/// Exception position index field length in bytes (u16).
/// 异常位置索引字段长度 (字节, u16)
pub const EXC_POS_LEN: usize = size_of::<u16>();

/// Number of sample points drawn during parameter search.
/// 参数推导搜索采样点数量
pub const SAMPLES_COUNT: usize = 32;

/// Early exit Bit-width threshold for early exit when 0 exceptions are found in parameter sampling.
/// 采样时当 0 异常且位宽不超过此门限时提前终止探测
pub const EARLY_EXIT_BIT_WIDTH: usize = 8;

/// Lookup table size for 1-bit unpacking.
/// 1 比特解包查找表大小
pub const LUT_SIZE_1BIT: usize = 2;

/// Lookup table size for 2-bit unpacking.
/// 2 比特解包查找表大小
pub const LUT_SIZE_2BIT: usize = 4;

/// Lookup table size for 4-bit unpacking.
/// 4 比特解包查找表大小
pub const LUT_SIZE_4BIT: usize = 16;

/// Lookup table size for 8-bit unpacking.
/// 8 比特解包查找表大小
pub const LUT_SIZE_8BIT: usize = 256;

/// Static positive power table for f64 (10^0 .. 10^18).
/// f64 静态正幂表 10^0 .. 10^18
pub const EXP_ARR_F64: [f64; 19] = [
  1.0,
  10.0,
  100.0,
  1_000.0,
  10_000.0,
  100_000.0,
  1_000_000.0,
  10_000_000.0,
  100_000_000.0,
  1_000_000_000.0,
  10_000_000_000.0,
  100_000_000_000.0,
  1_000_000_000_000.0,
  10_000_000_000_000.0,
  100_000_000_000_000.0,
  1_000_000_000_000_000.0,
  10_000_000_000_000_000.0,
  100_000_000_000_000_000.0,
  1_000_000_000_000_000_000.0,
];

/// Static negative power table for f64 (10^-0 .. 10^-18).
/// f64 静态负幂表 10^-0 .. 10^-18
pub const FRAC_ARR_F64: [f64; 19] = [
  1.0,
  0.1,
  0.01,
  0.001,
  0.0001,
  0.00001,
  0.000001,
  0.0000001,
  0.00000001,
  0.000000001,
  0.0000000001,
  0.00000000001,
  0.000000000001,
  0.0000000000001,
  0.00000000000001,
  0.000000000000001,
  0.0000000000000001,
  0.00000000000000001,
  0.000000000000000001,
];

/// Static integer factor table for f64 (10^0 .. 10^18).
/// f64 静态整型因子表 10^0 .. 10^18
pub const FACT_ARR_F64: [i64; 19] = [
  1,
  10,
  100,
  1_000,
  10_000,
  100_000,
  1_000_000,
  10_000_000,
  100_000_000,
  1_000_000_000,
  10_000_000_000,
  100_000_000_000,
  1_000_000_000_000,
  10_000_000_000_000,
  100_000_000_000_000,
  1_000_000_000_000_000,
  10_000_000_000_000_000,
  100_000_000_000_000_000,
  1_000_000_000_000_000_000,
];

/// Static positive power table for f32 (10^0 .. 10^10).
/// f32 静态正幂表 10^0 .. 10^10
pub const EXP_ARR_F32: [f32; 11] = [
  1.0,
  10.0,
  100.0,
  1_000.0,
  10_000.0,
  100_000.0,
  1_000_000.0,
  10_000_000.0,
  100_000_000.0,
  1_000_000_000.0,
  10_000_000_000.0,
];

/// Static negative power table for f32 (10^-0 .. 10^-10).
/// f32 静态负幂表 10^-0 .. 10^-10
pub const FRAC_ARR_F32: [f32; 11] = [
  1.0,
  0.1,
  0.01,
  0.001,
  0.0001,
  0.00001,
  0.000001,
  0.0000001,
  0.00000001,
  0.000000001,
  0.0000000001,
];

/// Static integer factor table for f32 (10^0 .. 10^10).
/// f32 静态整型因子表 10^0 .. 10^10
pub const FACT_ARR_F32: [i64; 11] = [
  1,
  10,
  100,
  1_000,
  10_000,
  100_000,
  1_000_000,
  10_000_000,
  100_000_000,
  1_000_000_000,
  10_000_000_000,
];