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#ifndef lint |
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static const char RCSid[] = "$Id: RdataShareMap.cpp,v 2.4 2025/03/20 17:59:10 greg Exp $"; |
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#endif |
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/* |
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* RdataShareMap.cpp |
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* |
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* Shared data using memory-mapped file |
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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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#include "rtio.h" |
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#include "rterror.h" |
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#include "RdataShare.h" |
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#include <unistd.h> |
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#include <sys/stat.h> |
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#include <sys/mman.h> |
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|
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// Create memory-mapped file object |
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RdataShareMap::RdataShareMap(const char *name, int flags, size_t siz) |
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{ |
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mmorg = NULL; |
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bufCount = 0; |
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|
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if (!(flags & (RDSread|RDSwrite))) { |
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error(CONSISTENCY, "RdataShareMap() flags must include RDSread or RDSwrite"); |
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return; |
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} |
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if (name && !*name) name = NULL; |
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if (!name && !siz | ((flags & (RDSextend|RDSread|RDSwrite)) != |
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(RDSextend|RDSread|RDSwrite))) { |
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error(CONSISTENCY, "anonymous memory map must be read/write"); |
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return; |
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} |
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if ((flags & (RDSextend|RDSwrite)) == RDSextend) { |
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error(CONSISTENCY, "bad RDSextend in RdataShareMap()"); |
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return; |
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} |
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int oflags, mmprot; |
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switch (flags & (RDSread|RDSwrite)) { |
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case RDSread|RDSwrite: |
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mmprot = PROT_READ|PROT_WRITE; |
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oflags = O_RDWR|O_CREAT; |
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break; |
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case RDSwrite: |
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mmprot = PROT_WRITE; |
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oflags = O_RDWR|O_CREAT; // XXX system limitation |
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break; |
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case RDSread: |
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mmprot = PROT_READ; |
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oflags = O_RDONLY; |
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break; |
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} |
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int fd = -1; |
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if (name) { // opening a shared file |
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if (flags & RDSexcl) oflags |= O_EXCL; |
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else if (flags & RDSextend && !siz) oflags |= O_TRUNC; |
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fd = open(name, oflags, 0666); |
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if (fd < 0) { |
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sprintf(errmsg, "cannot open '%s'", name); |
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error(SYSTEM, errmsg); |
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return; |
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} |
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if (!(flags & RDSextend)) { |
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struct stat sbuf; |
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if (flags & RDSexcl) |
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siz = 0; |
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else if (fstat(fd, &sbuf) >= 0) |
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siz = sbuf.st_size; |
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else { |
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sprintf(errmsg, "cannot stat '%s'", name); |
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error(SYSTEM, errmsg); |
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close(fd); |
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return; |
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} |
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} else if (siz && ftruncate(fd, siz) < 0) { |
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sprintf(errmsg, "cannot resize '%s'", name); |
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error(SYSTEM, errmsg); |
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close(fd); |
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return; |
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} |
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} |
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if (siz) mmorg = (void *)mmap(NULL, siz, mmprot, |
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MAP_SHARED|(name ? MAP_FILE : MAP_ANON), fd, 0); |
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close(fd); |
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if (mmorg == MAP_FAILED) { |
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if (name) |
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sprintf(errmsg, "cannot map '%s' to memory", name); |
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else |
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sprintf(errmsg, "cannot map anonymous map of %ld KBytes", |
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long(siz/1024)); |
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error(SYSTEM, errmsg); |
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mmorg = NULL; |
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return; |
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} |
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osiz = siz; |
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if (name) chName = savqstr(name); |
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mode = flags; |
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} |
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|
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RdataShareMap::~RdataShareMap() |
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{ |
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if (mmorg) munmap(mmorg, osiz); |
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} |
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|
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// Attempt to extend or shrink object (adjust if 0) |
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size_t |
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RdataShareMap::Resize(size_t new_siz) |
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{ |
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if (new_siz > 0) { |
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if (new_siz == osiz) |
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return osiz; |
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if (!(mode & RDSwrite)) { |
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error(CONSISTENCY, "cannot resize read-only map"); |
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return 0; |
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} |
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} |
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if (bufCount > 0) { |
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error(INTERNAL, "cannot resize while memory is checked out"); |
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return 0; |
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} |
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if (!chName) { |
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if (!new_siz) // XXX should issue warning? |
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return osiz; |
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if (new_siz > osiz) { |
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error(INTERNAL, "cannot grow anonymous map"); |
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return 0; |
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} |
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return osiz = new_siz; // just pretend we shrank |
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} |
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if (!new_siz) { // sync to current file length? |
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struct stat sbuf; |
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if (stat(chName, &sbuf) < 0) { |
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sprintf(errmsg, "cannot stat '%s'", chName); |
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error(SYSTEM, errmsg); |
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return 0; |
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} |
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if (sbuf.st_size <= osiz) |
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return osiz = sbuf.st_size; |
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|
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new_siz = sbuf.st_size; |
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} |
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if (new_siz > osiz) { // need to extend & remap |
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int fd = open(chName, mode&RDSread ? O_RDWR : O_WRONLY); |
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if (fd < 0) { |
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sprintf(errmsg, "cannot reopen '%s'", chName); |
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error(SYSTEM, errmsg); |
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return 0; |
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} |
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if (ftruncate(fd, new_siz) < 0) { |
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sprintf(errmsg, "cannot grow '%s'", chName); |
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error(SYSTEM, errmsg); |
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close(fd); |
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return 0; |
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} |
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if (mmorg) munmap(mmorg, osiz); |
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mmorg = mmap(NULL, new_siz, |
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mode&RDSread ? PROT_READ|PROT_WRITE : PROT_WRITE, |
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MAP_SHARED|MAP_FILE, fd, 0); |
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close(fd); |
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if (mmorg == MAP_FAILED) { |
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sprintf(errmsg, "mmap() failed on '%s'", chName); |
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error(SYSTEM, errmsg); |
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mmorg = NULL; |
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return osiz = 0; |
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} |
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} else if (truncate(chName, new_siz) < 0) { |
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sprintf(errmsg, "cannot resize '%s'", chName); |
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return 0; |
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} |
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return osiz = new_siz; |
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} |
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|
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// Get data buffer |
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void * |
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RdataShareMap::GetMemory(size_t offs, size_t len, int fl) |
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{ |
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if (chName && fl & RDSextend) { // resize/extend? |
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if (offs + len > osiz ? !Resize(offs + len) : !Resize()) |
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return NULL; |
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} |
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if (offs + len > osiz) { |
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if (chName) |
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sprintf(errmsg, "requested block of %lu bytes outside map '%s'", |
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(unsigned long)len, chName); |
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else |
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sprintf(errmsg, "requested block of %lu bytes outside %lu byte map", |
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(unsigned long)len, (unsigned long)osiz); |
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error(CONSISTENCY, errmsg); |
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return NULL; |
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} |
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++bufCount; |
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return (char *)mmorg + offs; |
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} |
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|
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// Return data buffer |
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bool |
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RdataShareMap::ReleaseMemory(void *dp, int fl) |
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{ |
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if ((dp < mmorg) | ((char *)dp >= (char *)mmorg + osiz)) { |
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if (chName) |
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sprintf(errmsg, "returned block outside map '%s'", chName); |
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else |
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sprintf(errmsg, "returned block outside %lu byte map", |
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(unsigned long)osiz); |
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error(CONSISTENCY, errmsg); |
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return false; |
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} |
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bufCount -= (bufCount > 0); |
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return true; |
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} |
