第二章是关于数据类型, 向量, 矩阵, 原子数据类型, buffer, 纹理(texture), 采样器(sampler), 结构体. 还设计数据对齐和类型转换.

我们先来看看标量(Scalar).

2.1 标量(Scalar)

Metal支持 表1 中的数据类型. Metal不支持各种dobule, long类型. 包括: double, long, unsigned long, long long, unsigned long long, long double.

  • 表1 标量(Scalar)
类型 描述
bool 布尔类型, 值为true或false. The value true expands to the integer constant 1, and the value false expands to the integer constant 0.
char, int8_t A signed two’s complement 8-bit integer.
unsigned char, uchar, uint8_t 8-bit 整数
short, int16_t A signed two’s complement 16-bit integer.
unsigned short, ushort, uint16_t 16-bit无符号整数
int, int32_t A signed two’s complement 32-bit integer.
unsigned int, uint, uint32_t 32-bit 无符号整数
half 16-bit 浮点数. The half data type must conform to the IEEE 754 binary16 storage format.
float 32-bit 浮点数. The float data type must conform to the IEEE 754 single precision storage format.
size_t 64-bit 无符号整数. sizeof的返回值.
ptrdiff_t A signed integer type that is the result of subtracting two pointers. This is a 64-bit signed integer.
void 空

注意: Metal支持用f/F作为后缀来声明一个单精度浮点数, 用h/H声明一个半精度浮点数, 用u/U声明无符号整数字面量. 例如: 0.5f 0.5F 0.5h 0.5H

表2 大小和数据对齐大小

类型 大小(bytes, 字节) 对齐大小(bytes, 字节)
bool 1 1
char, int8_t, unsigned char, uchar, uint8_t 1 1
short, int16_t, unsigned short, ushort, uint16_t 2 2
int, int32_t, unsigned int, uint, uint32_t 4 4
half 2 2
float 4 4