io/FileDescriptor, net/SocketDescriptor: make lots of methods "const"

Only the file descriptor value itself is const, but the file itself
may be readable/writable.

src/io/FileDescriptor.cxx

@@ -185,7 +185,7 @@ FileDescriptor::CreatePipe(FileDescriptor &r, FileDescriptor &w) noexcept
 #ifdef _WIN32
 
 void
-FileDescriptor::SetBinaryMode() noexcept
+FileDescriptor::SetBinaryMode() const noexcept
 {
 	_setmode(fd, _O_BINARY);
 }
@@ -209,7 +209,7 @@ FileDescriptor::CreatePipeNonBlock(FileDescriptor &r,
 }
 
 void
-FileDescriptor::SetNonBlocking() noexcept
+FileDescriptor::SetNonBlocking() const noexcept
 {
 	assert(IsDefined());
 
@@ -218,7 +218,7 @@ FileDescriptor::SetNonBlocking() noexcept
 }
 
 void
-FileDescriptor::SetBlocking() noexcept
+FileDescriptor::SetBlocking() const noexcept
 {
 	assert(IsDefined());
 
@@ -227,7 +227,7 @@ FileDescriptor::SetBlocking() noexcept
 }
 
 void
-FileDescriptor::EnableCloseOnExec() noexcept
+FileDescriptor::EnableCloseOnExec() const noexcept
 {
 	assert(IsDefined());
 
@@ -236,7 +236,7 @@ FileDescriptor::EnableCloseOnExec() noexcept
 }
 
 void
-FileDescriptor::DisableCloseOnExec() noexcept
+FileDescriptor::DisableCloseOnExec() const noexcept
 {
 	assert(IsDefined());
 
@@ -251,7 +251,7 @@ FileDescriptor::Duplicate() const noexcept
 }
 
 bool
-FileDescriptor::CheckDuplicate(FileDescriptor new_fd) noexcept
+FileDescriptor::CheckDuplicate(FileDescriptor new_fd) const noexcept
 {
 	if (*this == new_fd) {
 		DisableCloseOnExec();
@@ -285,7 +285,7 @@ FileDescriptor::CreateSignalFD(const sigset_t *mask) noexcept
 #endif
 
 bool
-FileDescriptor::Rewind() noexcept
+FileDescriptor::Rewind() const noexcept
 {
 	assert(IsDefined());
 
@@ -302,7 +302,7 @@ FileDescriptor::GetSize() const noexcept
 }
 
 void
-FileDescriptor::FullRead(void *_buffer, std::size_t length)
+FileDescriptor::FullRead(void *_buffer, std::size_t length) const
 {
 	auto buffer = (std::byte *)_buffer;
 
@@ -320,7 +320,7 @@ FileDescriptor::FullRead(void *_buffer, std::size_t length)
 }
 
 void
-FileDescriptor::FullWrite(const void *_buffer, std::size_t length)
+FileDescriptor::FullWrite(const void *_buffer, std::size_t length) const
 {
 	auto buffer = (const std::byte *)_buffer;
 

src/io/FileDescriptor.hxx

@@ -151,36 +151,36 @@ public:
 	static bool CreatePipe(FileDescriptor &r, FileDescriptor &w) noexcept;
 
 #ifdef _WIN32
-	void EnableCloseOnExec() noexcept {}
-	void DisableCloseOnExec() noexcept {}
-	void SetBinaryMode() noexcept;
+	void EnableCloseOnExec() const noexcept {}
+	void DisableCloseOnExec() const noexcept {}
+	void SetBinaryMode() const noexcept;
 #else
 	static bool CreatePipeNonBlock(FileDescriptor &r,
 				       FileDescriptor &w) noexcept;
 
-	void SetBinaryMode() noexcept {}
+	void SetBinaryMode() const noexcept {}
 
 	/**
 	 * Enable non-blocking mode on this file descriptor.
 	 */
-	void SetNonBlocking() noexcept;
+	void SetNonBlocking() const noexcept;
 
 	/**
 	 * Enable blocking mode on this file descriptor.
 	 */
-	void SetBlocking() noexcept;
+	void SetBlocking() const noexcept;
 
 	/**
 	 * Auto-close this file descriptor when a new program is
 	 * executed.
 	 */
-	void EnableCloseOnExec() noexcept;
+	void EnableCloseOnExec() const noexcept;
 
 	/**
 	 * Do not auto-close this file descriptor when a new program
 	 * is executed.
 	 */
-	void DisableCloseOnExec() noexcept;
+	void DisableCloseOnExec() const noexcept;
 
 	/**
 	 * Duplicate this file descriptor.
@@ -203,7 +203,7 @@ public:
 	 * this method to inject file descriptors into a new child
 	 * process, to be used by a newly executed program.
 	 */
-	bool CheckDuplicate(FileDescriptor new_fd) noexcept;
+	bool CheckDuplicate(FileDescriptor new_fd) const noexcept;
 #endif
 
 #ifdef __linux__
@@ -223,13 +223,13 @@ public:
 	/**
 	 * Rewind the pointer to the beginning of the file.
 	 */
-	bool Rewind() noexcept;
+	bool Rewind() const noexcept;
 
-	off_t Seek(off_t offset) noexcept {
+	off_t Seek(off_t offset) const noexcept {
 		return lseek(Get(), offset, SEEK_SET);
 	}
 
-	off_t Skip(off_t offset) noexcept {
+	off_t Skip(off_t offset) const noexcept {
 		return lseek(Get(), offset, SEEK_CUR);
 	}
 
@@ -245,12 +245,13 @@ public:
 	off_t GetSize() const noexcept;
 
 #ifndef _WIN32
-	ssize_t ReadAt(off_t offset, void *buffer, std::size_t length) noexcept {
+	ssize_t ReadAt(off_t offset,
+		       void *buffer, std::size_t length) const noexcept {
 		return ::pread(fd, buffer, length, offset);
 	}
 #endif
 
-	ssize_t Read(void *buffer, std::size_t length) noexcept {
+	ssize_t Read(void *buffer, std::size_t length) const noexcept {
 		return ::read(fd, buffer, length);
 	}
 
@@ -258,9 +259,9 @@ public:
 	 * Read until all of the given buffer has been filled.  Throws
 	 * on error.
 	 */
-	void FullRead(void *buffer, std::size_t length);
+	void FullRead(void *buffer, std::size_t length) const;
 
-	ssize_t Write(const void *buffer, std::size_t length) noexcept {
+	ssize_t Write(const void *buffer, std::size_t length) const noexcept {
 		return ::write(fd, buffer, length);
 	}
 
@@ -268,7 +269,7 @@ public:
 	 * Write until all of the given buffer has been written.
 	 * Throws on error.
 	 */
-	void FullWrite(const void *buffer, std::size_t length);
+	void FullWrite(const void *buffer, std::size_t length) const;
 
 #ifndef _WIN32
 	int Poll(short events, int timeout) const noexcept;