X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=buffer_tree.h;h=549f95a224e1ede3ec8e5344d8beb87f3fb88e31;hp=abba7472d6407959ac2f09b59e8b43ba19b0dcda;hb=9b565c60fd159e12d255bb18db9dbff066deebea;hpb=fc100a582159c001bd5eb2244f314343309bb503 diff --git a/buffer_tree.h b/buffer_tree.h index abba7472..549f95a2 100644 --- a/buffer_tree.h +++ b/buffer_tree.h @@ -1,35 +1,24 @@ +/* + * Copyright (C) 2009-2010 Andre Noll + * + * Licensed under the GPL v2. For licencing details see COPYING. + */ + /** - * Buffer trees and buffer tree nodes. + * \file buffer_tree.h Buffer tree management. * + * \par Buffer trees and buffer tree nodes. * The buffer tree API offers a more powerful method than standard unix pipes * for managing the data flow from the producer of the data (e.g. the network * receiver) to its consumer(s) (e.g. a sound card). * - * Each data buffer starts its way from the root of the buffer tree. At each - * child node the data is investigated and new data is fed to each child. - * Everything happens within one single-treaded process. There are no file - * descriptors, no calls to read() or write(). - * - * A buffer tree consists of buffer tree nodes. Usually, there is exactly one - * node in the buffer tree, the root node, which has no parent. Every node - * different from the root node has exactly one parent. - * - * The root node represents a data source. Root nodes are thus used by the - * receivers of paraslash. Also, reading from stdin is realized as the root - * node of a buffer tree. + * A buffer tree consists of buffer tree nodes linked via certain parent/child + * relationships. * - * Each node may have arbitrary many children, including none. Nodes with no - * children are called leaf nodes. They represent a data sink, like the alsa or - * the file writer. - * - * Hence there are three different types of buffer tree nodes: The root node - * and the leaf nodes and nodes which have both a parent and at least one - * child. Such a node is called an internal node. - * - * Internal nodes represent filters through which data buffers flow, possibly - * while being altered on their way to the children of the node. Examples of - * internal nodes are audio file decoders (mp3dec, oggdec, ...), but also the - * check for a wav header is implemented as an internal buffer tree node. + * Each data buffer starts its way from the root of the buffer tree. At each + * node the data is investigated and possibly changed. New data is then fed to + * each child. Everything happens within one single-treaded process. There are + * no file descriptors and no calls to read() or write(). * * Whenever a node in the buffer tree creates output, either by creating a new * buffer or by pushing down buffers received from its parent, references to @@ -41,10 +30,7 @@ * For example, in para_audiod the alsa writer asks all parent nodes * for for the number of channels and the sample rate of the current * audio file. - */ -struct btr_node; - -/** + * * Buffer pools - An alternative to malloc/free buffer management. * * Non-leaf nodes usually create output to be processed by their children. The @@ -55,21 +41,21 @@ struct btr_node; * btr_add_output(). This adds references to that buffer to all children. The * buffer is automatically freed if no buffer tree node is using it any more. * - * This approach, while simple, has some drawbacks, especially affecting the - * root nodes of the buffer tree. Often the data source which is represented by - * a root node does not know in advance how much data will be available. - * Therefore the allocated buffer is either larger than what can currently be - * read, or is too small so that multiple buffers have to be used. + * This approach, while being simple, has some drawbacks, especially affecting + * the root nodes of the buffer tree. Often the data source which is + * represented by a root node does not know in advance how much data will be + * available. Therefore the allocated buffer is either larger than what can + * currently be read, or is too small so that multiple buffers have to be used. * * While this could be worked around by using a large buffer and calling * realloc() afterwards to shrink the buffer according to how much has been * read, there is a second problem which comes from the alignment constraints - * of some filters, mainly the decoders. These need a minimal amount of data to - * proceed, and most of them even need this amount as one contiguous buffer, - * i.e. not spread out over two or more buffers. + * of some filters, mainly the decoders like mp3dec. These need a minimal + * amount of data to proceed, and most of them even need this amount as one + * contiguous buffer, i.e. not spread out over two or more buffers. * * Although the buffer tree code handles this case just fine, it can be - * expensive because two or more buffers must be combined by copying buffer + * expensive because two or more buffers must be merged by copying buffer * contents around in order to satisfy the constraint. * * This is where buffer pools come into play. Buffer pools try to satisfy @@ -88,7 +74,7 @@ struct btr_node; * Child nodes consume data by working through their input queue, which is a * list of buffer references. Once the content of a buffer is no longer needed * by a child node, the child calls btr_consume() to indicate the amount of - * data which can be dropped from the child's point of view. If no reference + * data which can be dropped from the child's point of view. If no reference * to some region of the buffer pool area remains, the read head of the buffer * pool advances, making space available for the receiver node to fill. * @@ -100,21 +86,87 @@ struct btr_node; * is reached. */ +struct btr_node; struct btr_pool; -typedef int (*btr_command_handler)(struct btr_node *btrn, - const char *command, char **result); +/** + * The three different types of buffer tree nodes. + * + * Usually, there is exactly one node in the buffer tree, the root node, which + * has no parent. Every node different from the root node has exactly one + * parent. The root node represents a data source. Root nodes are thus used by + * the receivers of paraslash. Also, reading from stdin is realized as the root + * node of a buffer tree. + * + * Each node may have arbitrary many children, including none. Nodes with no + * children are called leaf nodes. They represent a data sink, like the alsa or + * the file writer. + * + * Hence there are three different types of buffer tree nodes: The root node + * and the leaf nodes and nodes which have both a parent and at least one + * child. Such a node is called an internal node. + * + * Internal nodes represent filters through which data buffers flow, possibly + * while being altered on their way to the children of the node. Examples of + * internal nodes are audio file decoders (mp3dec, oggdec, ...), but also the + * check for a wav header is implemented as an internal buffer tree node. + */ enum btr_node_type { + /* This node has no parent. */ BTR_NT_ROOT, + /* Node has parent and at least one child. */ BTR_NT_INTERNAL, + /* Node has no children. */ BTR_NT_LEAF, }; +/** + * Per node handler used for inter node communication. + * + * Each node in the buffer tree may optionally provide a command handler for + * execution of commands by other nodes of the tree. + * + * It is dependent on the node in question which commands are supported and how + * they work. In any case, the input for the command handler is some string and + * its output is also a string which is returned via the \a result pointer of + * the handler. + * + * This mechanism is used in para_audiod e.g. by the alsa writer which needs to + * know the sample rate of its input known to e.g. the mp3dec node further up + * in the buffer tree. + */ +typedef int (*btr_command_handler)(struct btr_node *btrn, + const char *command, char **result); + +/** + * Structure for creating new buffer tree nodes. + * + * btr_new_node() takes a pointer to such a structure. + * + * There are four different combinations of \a parent and child: + * + * 1. both \p NULL. This creates a new buffer tree with a single isolated node. + * + * 2. \a parent != \p NULL, \a child == NULL. This creates a new leaf node by + * adding the new node to the list of children of the given parent node. + * + * 3. \a parent == NULL, \a child != NULL. The new node becomes the new root of + * the buffer tree. The child must be old root. + * + * 4. both != NULL. This creates a new internal node. \a child must be child of + * p. This mode of operation is currently not needed and is thus not yet + * implemented. + */ struct btr_node_description { + /** Name of the new node. */ const char *name; + /** Parent of the new node. */ struct btr_node *parent; + /** Child of the new node. */ struct btr_node *child; + /** Used for inter node communication. Optional. */ btr_command_handler handler; + /** Points usually to the struct that contains the node pointer. */ void *context; }; @@ -122,7 +174,7 @@ size_t btr_pool_size(struct btr_pool *btrp); struct btr_pool *btr_pool_new(const char *name, size_t area_size); void btr_pool_free(struct btr_pool *btrp); size_t btr_pool_get_buffer(struct btr_pool *btrp, char **result); -void btr_pool_allocate(struct btr_pool *btrp, size_t size); +int btr_pool_get_buffers(struct btr_pool *btrp, struct iovec iov[2]); void btr_add_output_pool(struct btr_pool *btrp, size_t size, struct btr_node *btrn); size_t btr_pool_unused(struct btr_pool *btrp); @@ -133,21 +185,18 @@ struct btr_node *btr_new_node(struct btr_node_description *bnd); void btr_remove_node(struct btr_node *btrn); void btr_free_node(struct btr_node *btrn); void btr_add_output(char *buf, size_t size, struct btr_node *btrn); -bool btr_no_children(struct btr_node *btrn); -size_t btr_bytes_pending(struct btr_node *btrn); size_t btr_get_input_queue_size(struct btr_node *btrn); +size_t btr_get_output_queue_size(struct btr_node *btrn); bool btr_no_parent(struct btr_node *btrn); size_t btr_next_buffer(struct btr_node *btrn, char **bufp); void btr_consume(struct btr_node *btrn, size_t numbytes); -int btr_exec(struct btr_node *btrn, const char *command, char **value_result); int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result); void btr_splice_out_node(struct btr_node *btrn); void btr_pushdown(struct btr_node *btrn); void *btr_context(struct btr_node *btrn); void btr_merge(struct btr_node *btrn, size_t dest_size); -bool btr_eof(struct btr_node *btrn); void btr_log_tree(struct btr_node *btrn, int loglevel); -int btr_pushdown_one(struct btr_node *btrn); +void btr_pushdown_one(struct btr_node *btrn); bool btr_inplace_ok(struct btr_node *btrn); int btr_node_status(struct btr_node *btrn, size_t min_iqs, enum btr_node_type type);