diff --git a/Makefile b/Makefile
line changes: +1/-1
index 40ebc63..c66d758
--- a/Makefile
+++ b/Makefile

@@ -13,7 +13,7 @@ HTTP_LIBDIRS = $(MHD_LIBDIR) $(YAJL_LIBDIR)
 CGI_LIBDIRS = $(CGI_UTIL_LIBDIR) $(YAJL_LIBDIR)
 
 targets = blerg.a blerg_auth.a blergtool blerglatest blerg.cgi perl-lib www/build/enyo-blerg.js
-blerg_a_objects = database/database.o database/tags.o database/util.o database/configuration.o database/subscription.o common/stringbucket.o
+blerg_a_objects = database/database.o database/tags.o database/util.o database/configuration.o database/subscription.o common/stringbucket.o common/stringring.o
 blerg_auth_a_objects = common/auth.o common/md5.o
 blergtool_objects = tools/blergtool.o blerg.a
 blerglatest_objects = tools/blerglatest.o blerg.a common/json.o

diff --git a/common/stringring.c b/common/stringring.c
line changes: +174/-0
index 0000000..c788db8
--- /dev/null
+++ b/common/stringring.c

@@ -0,0 +1,174 @@
+/* Blerg is (C) 2011 The Dominion of Awesome, and is distributed under a
+ * BSD-style license.  Please see the COPYING file for details.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <stringring.h>
+
+#define STRINGRING_DATA_CHECK() \
+	if (sh == NULL)         \
+		return 0;       \
+	if (data == NULL)       \
+		return 0;       \
+	if (data[0] == 0)       \
+		return 0;
+
+
+struct stringring_handle * stringring_open(const char *filename) {
+	struct stringring_handle *sh;
+	struct stat st;
+	int initialize = 0;
+
+	sh = malloc(sizeof(struct stringring_handle));
+	if (sh == NULL) {
+		perror("stringring_handle malloc");
+		return NULL;
+	}
+
+	sh->fd = open(filename, O_RDWR | O_CREAT, 0600);
+	flock(sh->fd, LOCK_EX);
+	if (sh->fd == -1) {
+		perror("stringring open");
+		goto stringring_open__open_failed;
+	}
+
+	fstat(sh->fd, &st);
+	if (st.st_size < sizeof(struct stringring)) {
+		ftruncate(sh->fd, sizeof(struct stringring));
+		initialize = 1;
+	}
+	sh->sr = mmap(NULL, sizeof(struct stringring), PROT_READ | PROT_WRITE, MAP_SHARED, sh->fd, 0);
+	if (sh->sr == MAP_FAILED) {
+		perror("stringring mmap");
+		goto stringring_open__map_failed;
+	}
+
+	if (initialize) {
+		stringring_clear(sh);
+	}
+	flock(sh->fd, LOCK_UN);
+
+	return sh;
+
+stringring_open__map_failed:
+	flock(sh->fd, LOCK_UN);
+	fclose(sh->fd);
+stringring_open__open_failed:
+	free(sh);
+	return NULL;
+}
+
+void stringring_close(struct stringring_handle *sh) {
+	if (sh == NULL)
+		return;
+
+	if (sh->sr != NULL)
+		munmap(sh->sr, sizeof(struct stringring));
+
+	if (sh->fd > -1)
+		close(sh->fd);
+
+	free(sh);
+}
+
+int stringring_add(struct stringring_handle *sh, const char *data) {
+	STRINGRING_DATA_CHECK();
+
+	flock(sh->fd, LOCK_EX);
+	if (sh->sr->counter == 0) {
+		sh->sr->counter = STRINGRING_N_ENTRIES - 1;
+	} else {
+		sh->sr->counter--;
+	}
+
+	int data_len = strlen(data);
+	sh->sr->entries[sh->sr->counter].timestamp = time(NULL);
+	strncpy(sh->sr->entries[sh->sr->counter].data, data, STRINGRING_DATA_SIZE);
+	if (data_len < STRINGRING_DATA_SIZE) {
+		/* zero out the rest of the data */
+		memset(sh->sr->entries[sh->sr->counter].data + data_len, 0, STRINGRING_DATA_SIZE - data_len);
+	}
+	flock(sh->fd, LOCK_UN);
+
+	return 1;
+}
+
+int stringring_find_unlocked(struct stringring_handle *sh, const char *data, uint64_t cutoff) {
+	int n, i;
+
+	i = sh->sr->counter;
+	for (n = 0; n < STRINGRING_N_ENTRIES; n++) {
+		if (sh->sr->entries[i].timestamp > 0 &&
+		    sh->sr->entries[i].timestamp > cutoff &&
+		    strncmp(sh->sr->entries[i].data, data, STRINGRING_DATA_SIZE) == 0) {
+			return i;
+		}
+		i = (i + 1) % STRINGRING_N_ENTRIES;
+	}
+
+	return -1;
+}
+
+int stringring_find(struct stringring_handle *sh, const char *data, unsigned int max_age) {
+	int ret;
+	uint64_t cutoff = (max_age > 0 ? time(NULL) - max_age : 0);
+
+	flock(sh->fd, LOCK_SH);
+	ret = stringring_find_unlocked(sh, data, cutoff);
+	flock(sh->fd, LOCK_UN);
+
+	return ret;
+}
+
+int stringring_remove_index_unlocked(struct stringring_handle *sh, int idx) {
+	if (sh == NULL)
+		return 0;
+	if (idx < 0 || idx >= STRINGRING_N_ENTRIES)
+		return 0;
+
+	sh->sr->entries[idx].timestamp = 0;
+	memset(sh->sr->entries[idx].data, 0, STRINGRING_DATA_SIZE);
+
+	return 1;
+}
+
+int stringring_remove_index(struct stringring_handle *sh, int idx) {
+	int ret;
+
+	flock(sh->fd, LOCK_EX);
+	ret = stringring_remove_index_unlocked(sh, idx);
+	flock(sh->fd, LOCK_UN);
+
+	return ret;
+}
+
+int stringring_remove(struct stringring_handle *sh, const char *data) {
+	STRINGRING_DATA_CHECK();
+	int ret;
+
+	flock(sh->fd, LOCK_EX);
+	ret = stringring_remove_index_unlocked(sh,
+			stringring_find_unlocked(sh, data, 0));
+	flock(sh->fd, LOCK_UN);
+
+	return ret;
+}
+
+int stringring_clear(struct stringring_handle *sh) {
+	if (sh == NULL)
+		return 0;
+
+	flock(sh->fd, LOCK_EX);
+	memset(sh->sr, 0, sizeof(struct stringring));
+	flock(sh->fd, LOCK_UN);
+
+	return 1;
+}

diff --git a/common/stringring.h b/common/stringring.h
line changes: +30/-0
index 0000000..7aedeb4
--- /dev/null
+++ b/common/stringring.h

@@ -0,0 +1,30 @@
+#ifndef _STRINGRING_H
+#define _STRINGRING_H
+
+#include <stdint.h>
+
+#define STRINGRING_DATA_SIZE 32
+#define STRINGRING_N_ENTRIES 102
+
+struct stringring {
+	uint8_t counter;
+	uint8_t reserved[15];
+	struct {
+		uint64_t timestamp;
+		uint8_t data[STRINGRING_DATA_SIZE];
+	} entries[STRINGRING_N_ENTRIES];
+};
+
+struct stringring_handle {
+	int fd;
+	struct stringring *sr;
+};
+
+struct stringring_handle * stringring_open(const char *filename);
+void stringring_close(struct stringring_handle *sh);
+int stringring_add(struct stringring_handle *sh, const char *data);
+int stringring_find(struct stringring_handle *sh, const char *data, unsigned int max_age);
+int stringring_remove(struct stringring_handle *sh, const char *data);
+int stringring_clear(struct stringring_handle *sh);
+
+#endif /* _STRINGRING_H */