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104a6e9788
In a subsequent commit we're going to add the first caller to writev(3p). Introduce a compatibility wrapper for this syscall that we can use on systems that don't have this syscall. The syscall exists on modern Unixes like Linux and macOS, and seemingly even for NonStop according to [1]. It doesn't seem to exist on Windows though. [1]: http://nonstoptools.com/manuals/OSS-SystemCalls.pdf [2]: https://www.gnu.org/software/gnulib/manual/html_node/writev.html Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
45 lines
1.0 KiB
C
45 lines
1.0 KiB
C
#include "../git-compat-util.h"
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#include "../wrapper.h"
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ssize_t git_writev(int fd, const struct iovec *iov, int iovcnt)
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{
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size_t total_written = 0;
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size_t sum = 0;
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/*
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* According to writev(3p), the syscall shall error with EINVAL in case
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* the sum of `iov_len` overflows `ssize_t`.
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*/
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for (int i = 0; i < iovcnt; i++) {
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if (iov[i].iov_len > maximum_signed_value_of_type(ssize_t) ||
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iov[i].iov_len + sum > maximum_signed_value_of_type(ssize_t)) {
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errno = EINVAL;
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return -1;
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}
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sum += iov[i].iov_len;
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}
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for (int i = 0; i < iovcnt; i++) {
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const char *bytes = iov[i].iov_base;
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size_t iovec_written = 0;
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while (iovec_written < iov[i].iov_len) {
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ssize_t bytes_written = xwrite(fd, bytes + iovec_written,
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iov[i].iov_len - iovec_written);
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if (bytes_written < 0) {
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if (total_written)
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goto out;
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return bytes_written;
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}
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if (!bytes_written)
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goto out;
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iovec_written += bytes_written;
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total_written += bytes_written;
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}
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}
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out:
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return (ssize_t) total_written;
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}
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