1 files changed, 52 insertions, 0 deletions
diff --git a/accent.h b/accent.h
new file mode 100644
index 0000000..8c9c6d4
--- /dev/null
+++ b/accent.h
@@ -0,0 +1,52 @@
+#ifndef ACCENT_H
+#define ACCENT_H
+#include <stdint.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#define SHMNAME "/breathing_color_shm"
+#define SHM_MAGIC 0xBEEFCAFEu
+#define SHM_VERSION 1u
+
+typedef struct {
+    uint32_t magic;
+    uint32_t version;
+    volatile uint32_t seq;
+    char color[8];
+} ColorShm;
+
+static inline ColorShm *
+mapaccent(void)
+{
+    int fd;
+    ColorShm *blk;
+    if ((fd = shm_open(SHMNAME, O_RDONLY, 0)) < 0)
+        return NULL;
+    blk = mmap(NULL, sizeof(ColorShm), PROT_READ, MAP_SHARED, fd, 0);
+    close(fd);
+    if (blk == MAP_FAILED)
+        return NULL;
+    if (blk->magic != SHM_MAGIC || blk->version != SHM_VERSION) {
+        munmap(blk, sizeof(ColorShm));
+        return NULL;
+    }
+    return blk;
+}
+
+static inline int
+readaccent(ColorShm **blk, char out[8])
+{
+    uint32_t s1, s2;
+    if (!*blk && !(*blk = mapaccent()))
+        return 0;
+    do {
+        s1 = (*blk)->seq;
+        memcpy(out, (*blk)->color, 8);
+        s2 = (*blk)->seq;
+    } while (s1 != s2);
+    return out[0] == '#';
+}
+
+#endif /* ACCENT_H */