Open/close attribute support for xattrs backend

For the xattr/BSD (untyped) attribute backend implement fs_fopen_attr()
and fs_close_attr(). A new AttributeDescriptor is created. It is
currently used in write_pos() only.

src/build/libroot/fs.cpp

@@ -969,12 +969,25 @@ read_pos(int fd, off_t pos, void *buffer, size_t bufferSize)
 ssize_t
 write_pos(int fd, off_t pos, const void *buffer, size_t bufferSize)
 {
+	// If this is an attribute descriptor, let it do the job.
+	AttributeDescriptor* descriptor
+		= dynamic_cast<AttributeDescriptor*>(get_descriptor(fd));
+	if (descriptor != NULL) {
+		status_t error = descriptor->Write(pos, buffer, bufferSize);
+		if (error != B_OK) {
+			errno = error;
+			return -1;
+		}
+
+		return 0;
+	}
+
 	// seek
 	off_t result = lseek(fd, pos, SEEK_SET);
 	if (result < 0)
 		return errno;
 
-	// read
+	// write
 	ssize_t bytesWritten = haiku_host_platform_write(fd, buffer, bufferSize);
 	if (bytesWritten < 0) {
 		errno = bytesWritten;

src/build/libroot/fs_attr_generic.cpp

@@ -309,9 +309,9 @@ fs_rewind_attr_dir(DIR *dir)
 	rewinddir(dir);
 }
 
-// fs_open_attr
+// fs_fopen_attr
 int
-fs_open_attr(int fd, const char *attribute, uint32 type, int openMode)
+fs_fopen_attr(int fd, const char *attribute, uint32 type, int openMode)
 {
 	if (!attribute) {
 		errno = B_BAD_VALUE;

src/build/libroot/fs_attr_untyped.cpp

@@ -452,22 +452,50 @@ fs_rewind_attr_dir(DIR *dir)
 		attrDir->RewindDir();
 }
 
-// fs_open_attr
+// fs_fopen_attr
 int
-fs_open_attr(int fd, const char *attribute, uint32 type, int openMode)
+fs_fopen_attr(int fd, const char *attribute, uint32 type, int openMode)
 {
-	// not supported ATM
+	if (fd < 0) {
 		errno = B_BAD_VALUE;
 		return -1;
+	}
+
+	AttributeDescriptor* descriptor = new(std::nothrow) AttributeDescriptor(fd,
+		attribute, type, openMode);
+	if (descriptor == NULL) {
+		errno = B_NO_MEMORY;
+		return -1;
+	}
+
+	status_t error = descriptor->Init();
+	if (error != B_OK) {
+		delete descriptor;
+		errno = error;
+		return -1;
+	}
+
+	int attributeFD = add_descriptor(descriptor);
+	if (attributeFD < 0) {
+		delete descriptor;
+		errno = B_NO_MEMORY;
+		return -1;
+	}
+
+	return attributeFD;
 }
 
 // fs_close_attr
 int
 fs_close_attr(int fd)
 {
-	// not supported ATM
+	status_t error = delete_descriptor(fd);
-	errno = B_BAD_VALUE;
+	if (error != 0) {
+		errno = error;
 		return -1;
+	}
+
+	return 0;
 }
 
 // fs_read_attr

src/build/libroot/fs_descriptors.cpp

@@ -11,7 +11,9 @@
 
 #include <map>
 
+#include <fcntl.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #include <fs_attr.h>
@@ -250,6 +252,151 @@ SymlinkDescriptor::GetPath(string& path) const
 }
 
 
+// #pragma mark - AttributeDescriptor
+
+
+AttributeDescriptor::AttributeDescriptor(int fileFD, const char* attribute,
+	uint32 type, int openMode)
+	:
+	fFileFD(dup(fileFD)),
+	fType(type),
+	fOpenMode(openMode),
+	fData(NULL),
+	fDataSize(0)
+
+{
+	strlcpy(fAttribute, attribute, sizeof(fAttribute));
+}
+
+
+AttributeDescriptor::~AttributeDescriptor()
+{
+	Close();
+}
+
+
+status_t
+AttributeDescriptor::Init()
+{
+	if (fFileFD < 0)
+		return B_IO_ERROR;
+
+	// stat the attribute
+	attr_info info;
+	if (fs_stat_attr(fFileFD, fAttribute, &info) < 0) {
+		if (errno == B_ENTRY_NOT_FOUND) {
+			if ((fOpenMode & O_CREAT) == 0)
+				return errno;
+
+			// create the attribute
+			if (fs_write_attr(fFileFD, fAttribute, fType, 0, NULL, 0) < 0)
+				return errno;
+			return B_OK;
+		}
+		return errno;
+	}
+
+	if ((fOpenMode & O_TRUNC) == 0) {
+		// truncate the attribute
+		if (fs_write_attr(fFileFD, fAttribute, fType, 0, NULL, 0) < 0)
+			return errno;
+		return B_OK;
+	}
+
+	// we have to read in the attribute data
+	if (info.size == 0)
+		return B_OK;
+
+	fData = (uint8*)malloc(info.size);
+	if (fData == NULL)
+		return B_NO_MEMORY;
+
+	fDataSize = info.size;
+
+	ssize_t bytesRead = fs_read_attr(fFileFD, fAttribute, fType, 0, fData,
+		fDataSize);
+	if (bytesRead < 0)
+		return errno;
+	if ((size_t)bytesRead != fDataSize)
+		return B_IO_ERROR;
+
+	return B_OK;
+}
+
+
+status_t
+AttributeDescriptor::Write(off_t offset, const void* buffer, size_t bufferSize)
+{
+	if (offset < 0)
+		return B_BAD_VALUE;
+
+	if ((fOpenMode & O_ACCMODE) != O_WRONLY
+		&& (fOpenMode & O_ACCMODE) != O_RDWR) {
+		return B_NOT_ALLOWED;
+	}
+
+	// we may need to resize the buffer
+	size_t minSize = (size_t)offset + bufferSize;
+	if (minSize > fDataSize) {
+		uint8* data = (uint8*)realloc(fData, minSize);
+		if (data == NULL)
+			return B_NO_MEMORY;
+
+		if ((size_t)offset > fDataSize)
+			memset(data + offset, 0, offset - fDataSize);
+
+		fData = data;
+		fDataSize = minSize;
+	}
+
+	// copy the data and write all of it
+	if (bufferSize == 0)
+		return B_OK;
+
+	memcpy((uint8*)fData + offset, buffer, bufferSize);
+
+	ssize_t bytesWritten = fs_write_attr(fFileFD, fAttribute, fType, 0,
+		fData, fDataSize);
+	if (bytesWritten < 0)
+		return errno;
+	if ((size_t)bytesWritten != fDataSize)
+		return B_IO_ERROR;
+
+	return B_OK;
+}
+
+
+status_t
+AttributeDescriptor::Close()
+{
+	if (fFileFD < 0)
+		return B_BAD_VALUE;
+
+	close(fFileFD);
+	fFileFD = -1;
+
+	free(fData);
+	fData = NULL;
+	fDataSize = 0;
+
+	return B_OK;
+}
+
+
+status_t
+AttributeDescriptor::Dup(Descriptor*& clone)
+{
+	return B_NOT_SUPPORTED;
+}
+
+
+status_t
+AttributeDescriptor::GetStat(bool traverseLink, struct stat* st)
+{
+	return B_NOT_SUPPORTED;
+}
+
+
 // #pragma mark - AttrDirDescriptor
 
 

src/build/libroot/fs_descriptors.h

@@ -5,6 +5,7 @@
 
 #include <string>
 
+#include <StorageDefs.h>
 #include <SupportDefs.h>
 
 #include "NodeRef.h"
@@ -71,6 +72,35 @@ struct SymlinkDescriptor : Descriptor {
 	virtual status_t GetPath(string& path) const;
 };
 
+// AttributeDescriptor
+struct AttributeDescriptor : Descriptor {
+								AttributeDescriptor(int fileFD,
+									const char* attribute, uint32 type,
+									int openMode);
+	virtual						~AttributeDescriptor();
+
+			status_t			Init();
+			status_t			Write(off_t offset, const void* buffer,
+									size_t bufferSize);
+
+			int					FileFD() const		{ return fFileFD; }
+			const char*			Attribute() const	{ return fAttribute; }
+			uint32				Type() const		{ return fType; }
+			int					OpenMode() const	{ return fOpenMode; }
+
+	virtual	status_t			Close();
+	virtual	status_t			Dup(Descriptor*& clone);
+	virtual	status_t			GetStat(bool traverseLink, struct stat* st);
+
+private:
+			int					fFileFD;
+			char				fAttribute[B_ATTR_NAME_LENGTH];
+			uint32				fType;
+			int					fOpenMode;
+			uint8*				fData;
+			size_t				fDataSize;
+};
+
 // AttrDirDescriptor
 struct AttrDirDescriptor : DirectoryDescriptor {