io/FileDescriptor: pass std::span to Full{Read,Write}()

src/io/FileDescriptor.cxx

@@ -249,38 +249,32 @@ FileDescriptor::GetSize() const noexcept
 }
 
 void
-FileDescriptor::FullRead(void *_buffer, std::size_t length) const
+FileDescriptor::FullRead(std::span<std::byte> dest) const
 {
-	auto buffer = (std::byte *)_buffer;
-
-	while (length > 0) {
-		ssize_t nbytes = Read(buffer, length);
+	while (!dest.empty()) {
+		ssize_t nbytes = Read(dest.data(), dest.size());
 		if (nbytes <= 0) {
 			if (nbytes < 0)
 				throw MakeErrno("Failed to read");
 			throw std::runtime_error("Unexpected end of file");
 		}
 
-		buffer += nbytes;
-		length -= nbytes;
+		dest = dest.subspan(nbytes);
 	}
 }
 
 void
-FileDescriptor::FullWrite(const void *_buffer, std::size_t length) const
+FileDescriptor::FullWrite(std::span<const std::byte> src) const
 {
-	auto buffer = (const std::byte *)_buffer;
-
-	while (length > 0) {
-		ssize_t nbytes = Write(buffer, length);
+	while (!src.empty()) {
+		ssize_t nbytes = Write(src.data(), src.size());
 		if (nbytes <= 0) {
 			if (nbytes < 0)
 				throw MakeErrno("Failed to write");
 			throw std::runtime_error("Failed to write");
 		}
 
-		buffer += nbytes;
-		length -= nbytes;
+		src = src.subspan(nbytes);
 	}
 }
 

src/io/FileDescriptor.hxx

@@ -4,6 +4,7 @@
 #pragma once
 
 #include <cstddef>
+#include <span>
 #include <utility>
 
 #include <unistd.h>
@@ -224,7 +225,7 @@ public:
 	 * Read until all of the given buffer has been filled.  Throws
 	 * on error.
 	 */
-	void FullRead(void *buffer, std::size_t length) const;
+	void FullRead(std::span<std::byte> dest) const;
 
 	ssize_t Write(const void *buffer, std::size_t length) const noexcept {
 		return ::write(fd, buffer, length);
@@ -234,7 +235,7 @@ public:
 	 * Write until all of the given buffer has been written.
 	 * Throws on error.
 	 */
-	void FullWrite(const void *buffer, std::size_t length) const;
+	void FullWrite(std::span<const std::byte> src) const;
 
 #ifndef _WIN32
 	int Poll(short events, int timeout) const noexcept;