Consider:
考虑：
ssize_t write(int fd, const void *buf, size_t count);
The result has to be signed to account for -1 on error, etc., and is thus ssize_t. But why then allow for the request to be an unsigned amount (twice as large) when the result of asking for more than ssize_t is undefined?
结果必须在错误等情况下签名为-1，因此是ssize_t。但是，当要求超过ssize_t的结果未定义时，为什么允许请求为无符号数量（两倍大）？
Is there a significant optimization in the kernel by virtue of not checking for signedness of the count parameter? Or something else?
由于没有检查计数参数的有效性，内核是否有重大的优化？或者是其他东西？
4 个解决方案
#1
6
According to the documentation for ssize_t write(int fildes, const void *buf, size_t nbyte)
根据ssize_t写的文档（int fildes，const void * buf，size_t nbyte）
If the value of nbyte is greater than {SSIZE_MAX}, the result is implementation-defined.
如果nbyte的值大于{SSIZE_MAX}，则结果是实现定义的。
So each particular implementation may handle this situation differently. I would not be surprised if some implementations simply set EFBIG.
因此，每个特定实现可以不同地处理这种情况如果某些实现只是设置EFBIG，我不会感到惊讶。
As for the rationale, perhaps size_t is simply the best type to represent the size of the buffer, semantically? It states that this argument is a nonnegative size, and nothing else.
至于基本原理，也许size_t只是表示缓冲区大小的最佳类型，从语义上来说呢？它声明这个论证是一个非负的大小，没有别的。
#2
5
I think it's nice, since size_t is the type of the value returned by the sizeof operator, this allows calls like this:
我认为这很好，因为size_t是sizeof运算符返回的值的类型，这允许这样的调用：
char buffer[1 << 20];
ssize_t wrote;
wrote = write(fd, buffer, sizeof buffer);
If the function took the signed version, a cast would be required. Also, as others have pointed out, semantically functions like these cannot accept a negative value, so it doesn't make a lot of sense to accept them.
如果函数采用签名版本，则需要进行强制转换。此外，正如其他人所指出的那样，语义上这些函数不能接受负值，因此接受它们并没有多大意义。
#3
2
By making the parameter unsigned it removes the need for the function to check for nonsensical negative requests.
通过使参数无符号，它不需要函数来检查无意义的否定请求。
#4
1
write can only write from a single contiguous array of unsigned char, which cannot be larger than PTRDIFF_MAX, which is (on all real-world POSIX systems, and perhaps this is required by POSIX too...?) equal to SIZE_MAX/2. Thus passing a value which would be negative if interpreted as a signed value is a programming error to begin with - the passed size does not agree with the available space in the buffer.
write只能从一个连续的无符号字符数组中写入，这个字符不能大于PTRDIFF_MAX，它是（在所有真实的POSIX系统上，也可能是POSIX所需要的......？）等于SIZE_MAX / 2。因此，如果解释为带符号值，则传递一个为负的值是一个编程错误 - 传递的大小与缓冲区中的可用空间不一致。
In theory readv and writev could perform IO operations larger than SIZE_MAX/2 by repeating the same iov buffers multiple times in the array, but if I remember correctly, they're specified to fail if the total size would be greater than SSIZE_MAX.
理论上，readv和writev可以通过在数组中多次重复相同的iov缓冲区来执行大于SIZE_MAX / 2的IO操作，但是如果我没记错的话，如果总大小将大于SSIZE_MAX，则指定它们失败。
#1
6
According to the documentation for ssize_t write(int fildes, const void *buf, size_t nbyte)
根据ssize_t写的文档（int fildes，const void * buf，size_t nbyte）
If the value of nbyte is greater than {SSIZE_MAX}, the result is implementation-defined.
如果nbyte的值大于{SSIZE_MAX}，则结果是实现定义的。
So each particular implementation may handle this situation differently. I would not be surprised if some implementations simply set EFBIG.
因此，每个特定实现可以不同地处理这种情况如果某些实现只是设置EFBIG，我不会感到惊讶。
As for the rationale, perhaps size_t is simply the best type to represent the size of the buffer, semantically? It states that this argument is a nonnegative size, and nothing else.
至于基本原理，也许size_t只是表示缓冲区大小的最佳类型，从语义上来说呢？它声明这个论证是一个非负的大小，没有别的。
#2
5
I think it's nice, since size_t is the type of the value returned by the sizeof operator, this allows calls like this:
我认为这很好，因为size_t是sizeof运算符返回的值的类型，这允许这样的调用：
char buffer[1 << 20];
ssize_t wrote;
wrote = write(fd, buffer, sizeof buffer);
If the function took the signed version, a cast would be required. Also, as others have pointed out, semantically functions like these cannot accept a negative value, so it doesn't make a lot of sense to accept them.
如果函数采用签名版本，则需要进行强制转换。此外，正如其他人所指出的那样，语义上这些函数不能接受负值，因此接受它们并没有多大意义。
#3
2
By making the parameter unsigned it removes the need for the function to check for nonsensical negative requests.
通过使参数无符号，它不需要函数来检查无意义的否定请求。
#4
1
write can only write from a single contiguous array of unsigned char, which cannot be larger than PTRDIFF_MAX, which is (on all real-world POSIX systems, and perhaps this is required by POSIX too...?) equal to SIZE_MAX/2. Thus passing a value which would be negative if interpreted as a signed value is a programming error to begin with - the passed size does not agree with the available space in the buffer.
write只能从一个连续的无符号字符数组中写入，这个字符不能大于PTRDIFF_MAX，它是（在所有真实的POSIX系统上，也可能是POSIX所需要的......？）等于SIZE_MAX / 2。因此，如果解释为带符号值，则传递一个为负的值是一个编程错误 - 传递的大小与缓冲区中的可用空间不一致。
In theory readv and writev could perform IO operations larger than SIZE_MAX/2 by repeating the same iov buffers multiple times in the array, but if I remember correctly, they're specified to fail if the total size would be greater than SSIZE_MAX.
理论上，readv和writev可以通过在数组中多次重复相同的iov缓冲区来执行大于SIZE_MAX / 2的IO操作，但是如果我没记错的话，如果总大小将大于SSIZE_MAX，则指定它们失败。