BamWriter

class BamWriter

Bases: BamEnums

This is the fundamental interface for writing binary objects to a Bam file, to be extracted later by a BamReader.

A Bam file can be thought of as a linear collection of objects. Each object is an instance of a class that inherits, directly or indirectly, from TypedWritable. The objects may include pointers to other objects; the BamWriter automatically manages these (with help from code within each class) and writes all referenced objects to the file in such a way that the pointers may be correctly restored later.

This is the abstract interface and does not specifically deal with disk files, but rather with a DatagramSink of some kind, which simply accepts a linear stream of Datagrams. It is probably written to a disk file, but it might conceivably be streamed directly to a network or some such nonsense.

Bam files are most often used to store scene graphs or subgraphs, and by convention they are given filenames ending in the extension “.bam” when they are used for this purpose. However, a Bam file may store any arbitrary list of TypedWritable objects; in this more general usage, they are given filenames ending in “.boo” to differentiate them from the more common scene graph files.

See also BamFile, which defines a higher-level interface to read and write Bam files on disk.

Inheritance diagram

explicit BamWriter(DatagramSink *target = nullptr)

BamWriter(BamWriter const&) = default

void flush(void)

Ensures that all data written thus far is manifested on the output stream.

BamEnums::BamEndian get_file_endian(void) const

Returns the endian preference indicated by the Bam file currently being written. This does not imply that every number is stored using the indicated convention, but individual objects may choose to respect this flag when recording data.

int get_file_major_ver(void) const

Returns the major version number of the Bam file currently being written.

int get_file_minor_ver(void) const

Returns the minor version number of the Bam file currently being written.

bool get_file_stdfloat_double(void) const

Returns true if the file will store all “standard” floats as 64-bit doubles, or false if they are 32-bit floats. This isn’t runtime settable; it’s based on the compilation flags of the version of Panda that generated this file.

BamEnums::BamTextureMode get_file_texture_mode(void) const

Returns the BamTextureMode preference indicated by the Bam file currently being written. Texture objects written to this Bam file will be encoded according to the specified mode.

Filename const &get_filename(void) const

If a BAM is a file, then the BamWriter should contain the name of the file. This enables the writer to convert pathnames in the BAM to relative to the directory containing the BAM.

TypedWritable *get_root_node(void) const

Returns the root node of the part of the scene graph we are currently writing out. This is used for determining what to make NodePaths relative to.

DatagramSink *get_target(void)

Returns the current target of the BamWriter as set by set_target() or the constructor.

bool has_object(TypedWritable const *obj) const

Returns true if the object has previously been written (or at least requested to be written) to the bam file, or false if we’ve never heard of it before.

bool init(void)

Initializes the BamWriter prior to writing any objects to its output stream. This includes writing out the Bam header.

This returns true if the BamWriter successfully initialized, false otherwise.

void set_file_minor_ver(int minor_ver)

Changes the minor .bam version to write. This should be called before init(). Each Panda version has only a fairly narrow range of versions it is able to write; consult the .bam documentation for more information.

void set_file_texture_mode(BamEnums::BamTextureMode file_texture_mode)

Changes the BamTextureMode preference for the Bam file currently being written. Texture objects written to this Bam file will be encoded according to the specified mode.

void set_root_node(TypedWritable *root_node)

Sets the root node of the part of the scene graph we are currently writing out. NodePaths written to this bam file will be relative to this node.

void set_target(DatagramSink *target)

Changes the destination of future datagrams written by the BamWriter. This also implicitly calls init() if it has not already been called.

bool write_object(TypedWritable const *obj)

Writes a single object to the Bam file, so that the BamReader::read_object() can later correctly restore the object and all its pointers.

This implicitly also writes any additional objects this object references (if they haven’t already been written), so that pointers may be fully resolved.

This may be called repeatedly to write a sequence of objects to the Bam file, but typically (especially for scene graph files, indicated with the .bam extension), only one object is written directly from the Bam file: the root of the scene graph. The remaining objects will all be written recursively by the first object.

Returns true if the object is successfully written, false otherwise.