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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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|
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#ifndef RdataShare_h |
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#define RdataShare_h |
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|
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#include <sys/types.h> |
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|
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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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/* |
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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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|
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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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|
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extern const char RDSnoname[]; |
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|
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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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|
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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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|
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struct RDSbuffer; // Private struct for buffer list |
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|
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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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|
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#endif // RdataShare_h |
