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/* RCSid $Id$ */
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/*
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* RdataShare.h
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*
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* Radiance classes for interprocess data sharing
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*
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* Errors end up calling error() from rterror.h, so
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* checking return values is not normally needed.
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*
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* Created by Greg Ward on 10/14/2024.
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*/
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#ifndef RdataShare_h
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#define RdataShare_h
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#include <sys/types.h>
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/// Channel creation and i/o flags
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enum {RDSexcl=1, RDSextend=2, RDSread=4, RDSwrite=8};
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/*
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* When data sharing object is created, flag meanings are:
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* RDSexcl = Create a new file, or fail if it exists
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* RDSextend = Set data extent to match size parameter
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* RDSread = Data may be read
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* RDSwrite = Data may be written
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*
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* The RDSread flag should be given to GetMemory() if a data
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* read operation is desired. Similarly, the RDSwrite flag
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* should be given when writing data in ReleaseMemory().
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* Memory-mapped files always read *and* write data if opened
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* in the appropriate mode. (Beware that writing to read-only data
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* or reading write-only data will generate a system fault.)
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* The RDSextend flag may be given with RDSread in GetMemory()
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* and RDSwrite in ReleaseMemory() to allow the file size to
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* increase as needed for a given operation.
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* In some implementations, the RDSexcl flag may guarantee
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* data consistency by placing locks on the requested memory areas.
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* In such cases, it may make sense to include the RDSwrite flag
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* in GetMemory() calls if the intention is to write new results
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* in ReleaseMemory(), so an exclusive lock will be held.
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*/
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/// Data share object types returned by GetType()
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enum RDSType {RDSTanonMap=1, RDSTfileMap, RDSTfile,
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RDSTcust1, RDSTcust2, RDSTcust3, RDSTcust4};
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extern const char RDSnoname[];
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/// Abstract base class for shared memory object
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class RdataShare {
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protected:
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char * chName; // channel name
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size_t osiz; // current object size
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int mode; // open mode
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public:
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RdataShare() {
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chName = NULL; osiz = 0; mode = 0;
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}
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virtual ~RdataShare();
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/// Get channel name, or RDSnoname if anonymous
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const char * GetName() const {
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return chName ? chName : RDSnoname;
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}
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/// Get R/W flags
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int GetMode() const {
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return mode & (RDSread|RDSwrite);
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}
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/// Get current object size
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size_t GetSize() const {
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return osiz;
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}
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/// Return data sharing type
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virtual RDSType GetType() const = 0;
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/// Attempt to extend or shrink object (adjust if 0)
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virtual size_t Resize(size_t new_siz = 0) = 0;
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/// Get data buffer
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virtual void * GetMemory(size_t offs, size_t len, int fl = RDSread) = 0;
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/// Return data buffer
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virtual bool ReleaseMemory(void *bp, int fl = RDSwrite) = 0;
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};
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/// Memory sharing implemented with mmap'ed file (or anonymous area)
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class RdataShareMap : public RdataShare {
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void * mmorg; // memory-mapped origin
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int bufCount; // count of allocated buffers
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public:
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RdataShareMap(const char *name, int flags, size_t siz = 0);
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virtual ~RdataShareMap();
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RDSType GetType() const {
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return chName ? RDSTfileMap : RDSTanonMap;
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}
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size_t Resize(size_t new_siz = 0);
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void * GetMemory(size_t offs, size_t len, int fl);
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bool ReleaseMemory(void *dp, int fl);
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};
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struct RDSbuffer; // Private struct for buffer list
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/// Memory sharing implemented with simple file
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class RdataShareFile : public RdataShare {
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int fd; // open file descriptor
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RDSbuffer * blist; // allocated buffer list
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public:
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RdataShareFile(const char *name, int flags, size_t siz = 0);
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virtual ~RdataShareFile();
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RDSType GetType() const {
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return RDSTfile;
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}
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size_t Resize(size_t new_siz = 0);
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void * GetMemory(size_t offs, size_t len, int fl);
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bool ReleaseMemory(void *dp, int fl);
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};
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#endif // RdataShare_h
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