# BamCache¶

class BamCache

This class maintains a cache of Bam and/or Txo objects generated from model files and texture images (as well as possibly other kinds of loadable objects that can be stored in bam file format).

This class also maintains a persistent index that lists all of the cached objects (see BamCacheIndex). We go through some considerable effort to make sure this index gets saved correctly to disk, even in the presence of multiple different processes writing to the same index, and without relying too heavily on low-level os-provided file locks (which work poorly with C++ iostreams).

Inheritance diagram

BamCache(void)
void consider_flush_global_index(void)

If there is a global BamCache object, calls consider_flush_index() on it.

void consider_flush_index(void)

Flushes the index if enough time has elapsed since the index was last flushed.

void flush_global_index(void)

If there is a global BamCache object, calls flush_index() on it.

void flush_index(void)

Ensures the index is written to disk.

bool get_active(void) const

Returns true if the BamCache is currently active, false if it is not. “active” means that the cache should be consulted automatically on loads, “not active” means that objects should be loaded directly without consulting the cache.

This represents the global flag. Also see the individual cache_models, cache_textures, cache_compressed_textures flags.

bool get_cache_compiled_shaders(void) const

Returns whether compiled shader programs will be stored in the cache, as binary .txo files. See set_cache_compiled_shaders().

This also returns false if get_active() is false.

bool get_cache_compressed_textures(void) const

Returns whether compressed texture files will be stored in the cache, as compressed txo files. See set_cache_compressed_textures().

This also returns false if get_active() is false.

int get_cache_max_kbytes(void) const

Returns the maximum size, in kilobytes, which the cache is allowed to grow to. See set_cache_max_kbytes().

bool get_cache_models(void) const

Returns whether model files (e.g. egg files and bam files) will be stored in the cache, as bam files.

This also returns false if get_active() is false.

bool get_cache_textures(void) const

Returns whether texture files (e.g. egg files and bam files) will be stored in the cache, as txo files.

This also returns false if get_active() is false.

int get_flush_time(void) const

Returns the time in seconds between automatic flushes of the cache index.

BamCache *get_global_ptr(void)

Returns a pointer to the global BamCache object, which is used automatically by the ModelPool and TexturePool.

bool get_read_only(void) const

Returns true if the cache is in read-only mode. Normally, the cache starts in read-write mode. It can put itself into read-only mode automatically if it discovers that it does not have write access to the cache.

Filename get_root(void) const

Returns the current root pathname of the cache. See set_root().

void list_index(std::ostream &out, int indent_level = 0) const

Writes the contents of the index to standard output.

PointerTo<BamCacheRecord> lookup(Filename const &source_filename, std::string const &cache_extension)

Looks up a file in the cache.

If the file is cacheable, then regardless of whether the file is found in the cache or not, this returns a BamCacheRecord. On the other hand, if the file cannot be cached, returns NULL.

If record->has_data() returns true, then the file was found in the cache, and you may call record->extract_data() to get the object. If record->has_data() returns false, then the file was not found in the cache or the cache was stale; and you should reload the source file (calling record->add_dependent_file() for each file loaded, including the original source file), and then call record->set_data() to record the resulting loaded object; and finally, you should call store() to write the cached record to disk.

void set_active(bool flag)

Changes the state of the active flag. “active” means that the cache should be consulted automatically on loads, “not active” means that objects should be loaded directly without consulting the cache.

This represents the global flag. Also see the individual cache_models, cache_textures, cache_compressed_textures flags.

void set_cache_compiled_shaders(bool flag)

Indicates whether compiled shader programs will be stored in the cache, as binary .sho files. This may not be supported by all shader languages or graphics renderers.

void set_cache_compressed_textures(bool flag)

Indicates whether compressed texture files will be stored in the cache, as compressed txo files. The compressed data may either be generated in-CPU, via the squish library, or it may be extracted from the GSG after the texture has been loaded.

This may be set in conjunction with set_cache_textures(), or independently of it. If set_cache_textures() is true and this is false, all textures will be cached in their uncompressed form. If set_cache_textures() is false and this is true, only compressed textures will be cached, and they will be cached in their compressed form. If both are true, all textures will be cached, in their uncompressed or compressed form appropriately.

void set_cache_max_kbytes(int max_kbytes)

Specifies the maximum size, in kilobytes, which the cache is allowed to grow to. If a newly cached file would exceed this size, an older file is removed from the cache.

Note that in the case of multiple different processes simultaneously operating on the same cache directory, the actual cache size may slightly exceed this value from time to time due to latency in checking between the processes.

void set_cache_models(bool flag)

Indicates whether model files (e.g. egg files and bam files) will be stored in the cache, as bam files.

void set_cache_textures(bool flag)

Indicates whether texture files will be stored in the cache, as uncompressed txo files.

void set_flush_time(int flush_time)

Specifies the time in seconds between automatic flushes of the cache index.

void set_read_only(bool ro)

Can be used to put the cache in read-only mode, or take it out of read-only mode. Note that if you put it into read-write mode, and it discovers that it does not have write access, it will put itself right back into read-only mode.

void set_root(Filename const &root)

Changes the current root pathname of the cache. This specifies where the cache files are stored on disk. This should name a directory that is on a disk local to the machine (not on a network-mounted disk), for instance, /tmp/panda-cache or /c/panda-cache.

If the directory does not already exist, it will be created as a result of this call.

bool store(BamCacheRecord *record)

Flushes a cache entry to disk. You must have retrieved the cache record via a prior call to lookup(), and then stored the data via record->set_data(). Returns true on success, false on failure.