thodg/libgit2/src/filebuf.c

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• Hash : 1db9d2c3
  Author :
  Date : 2012-02-23T17:11:20
  

  Ensure that commits don't fail if committing content that already exists Making a commit that results in a blob that already exists in the ODB (i.e. committing something, then making a revert commit) will result in us trying to p_rename -> MoveFileExW a temp file into the existing ODB entry. Despite the MOVEFILE_REPLACE_EXISTING flag is passed in, Win32 does not care and fails it with STATUS_ACCESS_DENIED. To fix this, we p_unlink the ODB entry before attempting to rename it. This call will typically fail, but we don't care, we'll let the p_rename fail if the file actually does exist and we couldn't delete it for some reason (ACLs, etc).

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• src/filebuf.c

• /*
   * Copyright (C) 2009-2012 the libgit2 contributors
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  #include <stdarg.h>
  
  #include "common.h"
  #include "filebuf.h"
  #include "fileops.h"
  
  #define GIT_LOCK_FILE_MODE 0644
  
  static const size_t WRITE_BUFFER_SIZE = (4096 * 2);
  
  static int lock_file(git_filebuf *file, int flags)
  {
  	if (git_path_exists(file->path_lock) == 0) {
  		if (flags & GIT_FILEBUF_FORCE)
  			p_unlink(file->path_lock);
  		else
  			return git__throw(GIT_EOSERR, "Failed to lock file");
  	}
  
  	/* create path to the file buffer is required */
  	if (flags & GIT_FILEBUF_FORCE) {
  		/* XXX: Should dirmode here be configurable? Or is 0777 always fine? */
  		file->fd = git_futils_creat_locked_withpath(file->path_lock, 0777, GIT_LOCK_FILE_MODE);
  	} else {
  		file->fd = git_futils_creat_locked(file->path_lock, GIT_LOCK_FILE_MODE);
  	}
  
  	if (file->fd < 0)
  		return git__throw(GIT_EOSERR, "Failed to create lock");
  
  	if ((flags & GIT_FILEBUF_APPEND) && git_path_exists(file->path_original) == 0) {
  		git_file source;
  		char buffer[2048];
  		size_t read_bytes;
  
  		source = p_open(file->path_original, O_RDONLY);
  		if (source < 0)
  			return git__throw(GIT_EOSERR, "Failed to lock file. Could not open %s", file->path_original);
  
  		while ((read_bytes = p_read(source, buffer, 2048)) > 0) {
  			p_write(file->fd, buffer, read_bytes);
  			if (file->digest)
  				git_hash_update(file->digest, buffer, read_bytes);
  		}
  
  		p_close(source);
  	}
  
  	return GIT_SUCCESS;
  }
  
  void git_filebuf_cleanup(git_filebuf *file)
  {
  	if (file->fd >= 0)
  		p_close(file->fd);
  
  	if (file->fd >= 0 && file->path_lock && git_path_exists(file->path_lock) == GIT_SUCCESS)
  		p_unlink(file->path_lock);
  
  	if (file->digest)
  		git_hash_free_ctx(file->digest);
  
  	if (file->buffer)
  		git__free(file->buffer);
  
  	/* use the presence of z_buf to decide if we need to deflateEnd */
  	if (file->z_buf) {
  		git__free(file->z_buf);
  		deflateEnd(&file->zs);
  	}
  
  	if (file->path_original)
  		git__free(file->path_original);
  	if (file->path_lock)
  		git__free(file->path_lock);
  
  	memset(file, 0x0, sizeof(git_filebuf));
  	file->fd = -1;
  }
  
  GIT_INLINE(int) flush_buffer(git_filebuf *file)
  {
  	int result = file->write(file, file->buffer, file->buf_pos);
  	file->buf_pos = 0;
  	return result;
  }
  
  static int write_normal(git_filebuf *file, void *source, size_t len)
  {
  	int result = 0;
  
  	if (len > 0) {
  		result = p_write(file->fd, (void *)source, len);
  		if (file->digest)
  			git_hash_update(file->digest, source, len);
  	}
  
  	return result;
  }
  
  static int write_deflate(git_filebuf *file, void *source, size_t len)
  {
  	int result = Z_OK;
  	z_stream *zs = &file->zs;
  
  	if (len > 0 || file->flush_mode == Z_FINISH) {
  		zs->next_in = source;
  		zs->avail_in = (uInt)len;
  
  		do {
  			size_t have;
  
  			zs->next_out = file->z_buf;
  			zs->avail_out = (uInt)file->buf_size;
  
  			result = deflate(zs, file->flush_mode);
  			if (result == Z_STREAM_ERROR)
  				return git__throw(GIT_ERROR, "Failed to deflate input");
  
  			have = file->buf_size - (size_t)zs->avail_out;
  
  			if (p_write(file->fd, file->z_buf, have) < GIT_SUCCESS)
  				return git__throw(GIT_EOSERR, "Failed to write to file");
  
  		} while (zs->avail_out == 0);
  
  		assert(zs->avail_in == 0);
  
  		if (file->digest)
  			git_hash_update(file->digest, source, len);
  	}
  
  	return GIT_SUCCESS;
  }
  
  int git_filebuf_open(git_filebuf *file, const char *path, int flags)
  {
  	int error, compression;
  	size_t path_len;
  
  	assert(file && path);
  
  	if (file->buffer)
  		return git__throw(GIT_EINVALIDARGS, "Tried to reopen an open filebuf");
  
  	memset(file, 0x0, sizeof(git_filebuf));
  
  	file->buf_size = WRITE_BUFFER_SIZE;
  	file->buf_pos = 0;
  	file->fd = -1;
  
  	/* Allocate the main cache buffer */
  	file->buffer = git__malloc(file->buf_size);
  	if (file->buffer == NULL){
  		error = GIT_ENOMEM;
  		goto cleanup;
  	}
  
  	/* If we are hashing on-write, allocate a new hash context */
  	if (flags & GIT_FILEBUF_HASH_CONTENTS) {
  		if ((file->digest = git_hash_new_ctx()) == NULL) {
  			error = GIT_ENOMEM;
  			goto cleanup;
  		}
  	}
  
  	compression = flags >> GIT_FILEBUF_DEFLATE_SHIFT;
  
  	/* If we are deflating on-write, */
  	if (compression != 0) {
  		/* Initialize the ZLib stream */
  		if (deflateInit(&file->zs, compression) != Z_OK) {
  			error = git__throw(GIT_EZLIB, "Failed to initialize zlib");
  			goto cleanup;
  		}
  
  		/* Allocate the Zlib cache buffer */
  		file->z_buf = git__malloc(file->buf_size);
  		if (file->z_buf == NULL){
  			error = GIT_ENOMEM;
  			goto cleanup;
  		}
  
  		/* Never flush */
  		file->flush_mode = Z_NO_FLUSH;
  		file->write = &write_deflate;
  	} else {
  		file->write = &write_normal;
  	}
  
  	/* If we are writing to a temp file */
  	if (flags & GIT_FILEBUF_TEMPORARY) {
  		git_buf tmp_path = GIT_BUF_INIT;
  
  		/* Open the file as temporary for locking */
  		file->fd = git_futils_mktmp(&tmp_path, path);
  		if (file->fd < 0) {
  			git_buf_free(&tmp_path);
  			error = GIT_EOSERR;
  			goto cleanup;
  		}
  
  		/* No original path */
  		file->path_original = NULL;
  		file->path_lock = git_buf_detach(&tmp_path);
  
  		if (file->path_lock == NULL) {
  			error = GIT_ENOMEM;
  			goto cleanup;
  		}
  	} else {
  		path_len = strlen(path);
  
  		/* Save the original path of the file */
  		file->path_original = git__strdup(path);
  		if (file->path_original == NULL) {
  			error = GIT_ENOMEM;
  			goto cleanup;
  		}
  
  		/* create the locking path by appending ".lock" to the original */
  		file->path_lock = git__malloc(path_len + GIT_FILELOCK_EXTLENGTH);
  		if (file->path_lock == NULL) {
  			error = GIT_ENOMEM;
  			goto cleanup;
  		}
  
  		memcpy(file->path_lock, file->path_original, path_len);
  		memcpy(file->path_lock + path_len, GIT_FILELOCK_EXTENSION, GIT_FILELOCK_EXTLENGTH);
  
  		/* open the file for locking */
  		if ((error = lock_file(file, flags)) < GIT_SUCCESS)
  			goto cleanup;
  	}
  
  	return GIT_SUCCESS;
  
  cleanup:
  	git_filebuf_cleanup(file);
  	return git__rethrow(error, "Failed to open file buffer for '%s'", path);
  }
  
  int git_filebuf_hash(git_oid *oid, git_filebuf *file)
  {
  	int error;
  
  	assert(oid && file && file->digest);
  
  	if ((error = flush_buffer(file)) < GIT_SUCCESS)
  		return git__rethrow(error, "Failed to get hash for file");
  
  	git_hash_final(oid, file->digest);
  	git_hash_free_ctx(file->digest);
  	file->digest = NULL;
  
  	return GIT_SUCCESS;
  }
  
  int git_filebuf_commit_at(git_filebuf *file, const char *path, mode_t mode)
  {
  	git__free(file->path_original);
  	file->path_original = git__strdup(path);
  	if (file->path_original == NULL)
  		return GIT_ENOMEM;
  
  	return git_filebuf_commit(file, mode);
  }
  
  int git_filebuf_commit(git_filebuf *file, mode_t mode)
  {
  	int error;
  
  	/* temporary files cannot be committed */
  	assert(file && file->path_original);
  
  	file->flush_mode = Z_FINISH;
  	if ((error = flush_buffer(file)) < GIT_SUCCESS)
  		goto cleanup;
  
  	p_close(file->fd);
  	file->fd = -1;
  
  	if (p_chmod(file->path_lock, mode)) {
  		error = git__throw(GIT_EOSERR, "Failed to chmod locked file before committing");
  		goto cleanup;
  	}
  
  	p_unlink(file->path_original);
  
  	error = p_rename(file->path_lock, file->path_original);
  
  cleanup:
  	git_filebuf_cleanup(file);
  	if (error < GIT_SUCCESS)
  		return git__rethrow(error, "Failed to commit locked file from buffer");
  	return GIT_SUCCESS;
  }
  
  GIT_INLINE(void) add_to_cache(git_filebuf *file, const void *buf, size_t len)
  {
  	memcpy(file->buffer + file->buf_pos, buf, len);
  	file->buf_pos += len;
  }
  
  int git_filebuf_write(git_filebuf *file, const void *buff, size_t len)
  {
  	int error;
  	const unsigned char *buf = buff;
  
  	for (;;) {
  		size_t space_left = file->buf_size - file->buf_pos;
  
  		/* cache if it's small */
  		if (space_left > len) {
  			add_to_cache(file, buf, len);
  			return GIT_SUCCESS;
  		}
  
  		add_to_cache(file, buf, space_left);
  
  		if ((error = flush_buffer(file)) < GIT_SUCCESS)
  			return git__rethrow(error, "Failed to write to buffer");
  
  		len -= space_left;
  		buf += space_left;
  	}
  }
  
  int git_filebuf_reserve(git_filebuf *file, void **buffer, size_t len)
  {
  	int error;
  	size_t space_left = file->buf_size - file->buf_pos;
  
  	*buffer = NULL;
  
  	if (len > file->buf_size)
  		return GIT_ENOMEM;
  
  	if (space_left <= len) {
  		if ((error = flush_buffer(file)) < GIT_SUCCESS)
  			return git__rethrow(error, "Failed to reserve buffer");
  	}
  
  	*buffer = (file->buffer + file->buf_pos);
  	file->buf_pos += len;
  
  	return GIT_SUCCESS;
  }
  
  int git_filebuf_printf(git_filebuf *file, const char *format, ...)
  {
  	va_list arglist;
  	size_t space_left;
  	int len, error;
  	char *tmp_buffer;
  
  	space_left = file->buf_size - file->buf_pos;
  
  	do {
  		va_start(arglist, format);
  		len = p_vsnprintf((char *)file->buffer + file->buf_pos, space_left, format, arglist);
  		va_end(arglist);
  
  		if (len < 0)
  			return git__throw(GIT_EOSERR, "Failed to format string");
  
  		if ((size_t)len + 1 <= space_left) {
  			file->buf_pos += len;
  			return GIT_SUCCESS;
  		}
  
  		if ((error = flush_buffer(file)) < GIT_SUCCESS)
  			return git__rethrow(error, "Failed to output to buffer");
  
  		space_left = file->buf_size - file->buf_pos;
  
  	} while ((size_t)len + 1 <= space_left);
  
  	tmp_buffer = git__malloc(len + 1);
  	if (!tmp_buffer)
  		return GIT_ENOMEM;
  
  	va_start(arglist, format);
  	len = p_vsnprintf(tmp_buffer, len + 1, format, arglist);
  	va_end(arglist);
  
  	if (len < 0) {
  		git__free(tmp_buffer);
  		return git__throw(GIT_EOSERR, "Failed to format string");
  	}
  
  	error = git_filebuf_write(file, tmp_buffer, len);
  	git__free(tmp_buffer);
  
  	return error;
  }
  
  

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