Merge branch 'majestic' of github.com:GrammaticalFramework/gf-core into majestic

src/runtime/c/Makefile.am

@@ -10,6 +10,8 @@ pgfinclude_HEADERS = \
 libpgf_la_SOURCES = \
 	pgf/db.cxx \
 	pgf/db.h \
+	pgf/ipc.cxx \
+	pgf/ipc.h \
 	pgf/text.cxx \
 	pgf/text.h \
 	pgf/pgf.cxx \

src/runtime/c/pgf/ipc.cxx

@@ -0,0 +1,112 @@
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "pgf/data.h"
+
+typedef struct {
+    dev_t dev;
+    ino_t ino;
+    pthread_rwlock_t rwlock;
+} file_locks_entry;
+
+typedef struct {
+    pthread_mutex_t mutex;
+    file_locks_entry entries[];
+} file_locks;
+
+static char gf_runtime_locks[] = "/gf-runtime-locks";
+
+PGF_INTERNAL
+pthread_rwlock_t *pgf_acquire_file_rwlock(const char* file_path)
+{
+    int created = 0;
+
+    int fd =
+        shm_open(gf_runtime_locks, O_RDWR, 0);
+    if (errno == ENOENT) {
+        created = 1;
+        fd = shm_open(gf_runtime_locks, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+    }
+    if (fd < 0) {
+        throw pgf_systemerror(errno);
+    }
+
+    int pagesize  = getpagesize();
+    int n_entries = (pagesize - sizeof(file_locks))
+                            / sizeof(file_locks_entry);
+
+    if (ftruncate(fd, pagesize) != 0) {
+        throw pgf_systemerror(errno);
+    }
+
+    file_locks *locks =
+          (file_locks *)
+                 mmap(NULL, pagesize,
+                      PROT_READ|PROT_WRITE,
+                      MAP_SHARED,
+                      fd,0);
+    if (locks == MAP_FAILED) {
+        throw pgf_systemerror(errno);
+    }
+
+    if (created) {
+        pthread_mutexattr_t attr;
+        if (pthread_mutexattr_init(&attr)) {
+            throw pgf_systemerror(errno);
+        }
+        if (pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED)) {
+            throw pgf_systemerror(errno);
+        }
+        if (pthread_mutex_init(&locks->mutex, &attr)) {
+            throw pgf_systemerror(errno);
+        }
+
+        for (int i = 0; i < n_entries; i++) {
+            locks->entries[i].dev = 0;
+            locks->entries[i].ino = 0;
+        }
+    }
+
+    struct stat s;
+    if (stat(file_path, &s) != 0) {
+        throw pgf_systemerror(errno);
+    }
+
+    pthread_mutex_lock(&locks->mutex);
+
+    file_locks_entry *entry = NULL;
+    for (int i = 0; i < n_entries; i++) {
+        if ((locks->entries[i].dev == s.st_dev &&
+             locks->entries[i].ino == s.st_ino) ||
+            (locks->entries[i].dev == 0 &&
+             locks->entries[i].ino == 0 &&
+             entry == NULL)) {
+            entry = &locks->entries[i];
+        }
+    }
+
+    if (entry == NULL) {
+        throw pgf_error("Too many files");
+    }
+
+    if (entry->dev == 0 && entry->ino == 0) {
+        entry->dev = s.st_dev;
+        entry->ino = s.st_ino;
+
+        pthread_rwlockattr_t attr;
+        if (pthread_rwlockattr_init(&attr) != 0) {
+            throw pgf_systemerror(errno);
+        }
+        if (pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_SHARED) != 0) {
+            throw pgf_systemerror(errno);
+        }
+        if (pthread_rwlock_init(&entry->rwlock, &attr) != 0) {
+            throw pgf_systemerror(errno);
+        }
+    }
+
+    pthread_mutex_unlock(&locks->mutex);
+
+    return &entry->rwlock;
+}

src/runtime/c/pgf/ipc.h

@@ -0,0 +1,7 @@
+#ifndef IPC_H
+#define IPC_H
+
+PGF_INTERNAL_DECL
+pthread_rwlock_t *pgf_acquire_file_rwlock(const char* file_path);
+
+#endif