From cd9974671506959cef24a6f7f2b8fce2790653bf Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Fri, 25 Mar 2022 19:56:41 +0000
Subject: [PATCH] lib.[ch], dvd-sector-copy.c: Publish a couple of generally
 handy utilities.

---
 dvd-sector-copy.c | 24 ------------------------
 lib.c             |  6 ++++++
 lib.h             | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 24 deletions(-)

diff --git a/dvd-sector-copy.c b/dvd-sector-copy.c
index 6f14bb5..fe99587 100644
--- a/dvd-sector-copy.c
+++ b/dvd-sector-copy.c
@@ -8,30 +8,6 @@ static void usage(FILE *fp)
 	  prog);
 }
 
-static double tvdiff(const struct timeval *tv_lo,
-		     const struct timeval *tv_hi)
-{
-  return ((tv_hi->tv_sec - tv_lo->tv_sec) +
-	  (tv_hi->tv_usec - tv_lo->tv_usec)/1.0e6);
-}
-
-#define DEFVEC(vtype, etype)						\
-	typedef struct { etype *v; size_t n, sz; } vtype
-#define VEC_INIT { 0, 0, 0 }
-#define VEC_FREE(vv) do {						\
-  free((vv)->v); (vv)->v 0; (vv)->n = (vv)->sz = 0;			\
-} while (0)
-#define VEC_PUSH(p, vv) do {						\
-  size_t _want;								\
-  if ((vv)->n >= (vv)->sz) {						\
-    (vv)->sz = (vv)->sz ? 2*(vv)->sz : 32;				\
-    _want = (vv)->sz*sizeof(*(vv)->v);					\
-    (vv)->v = realloc((vv)->v, _want);					\
-    if (!(vv)->v) bail("out of memory allocating %zu bytes", _want);	\
-  }									\
-  (p) = &(vv)->v[(vv)->n++];						\
-} while (0)
-
 #define MAXFILES (1 + 2*99 + 1)
 struct file {
   ident id;
diff --git a/lib.c b/lib.c
index 55c4b48..7021661 100644
--- a/lib.c
+++ b/lib.c
@@ -111,6 +111,12 @@ void sit(double t)
   }
 }
 
+double tvdiff(const struct timeval *tv_lo, const struct timeval *tv_hi)
+{
+  return ((tv_hi->tv_sec - tv_lo->tv_sec) +
+	  (tv_hi->tv_usec - tv_lo->tv_usec)/1.0e6);
+}
+
 void carefully_write(int fd, const void *buf, size_t sz)
 {
   const unsigned char *p = buf;
diff --git a/lib.h b/lib.h
index ebb13ac..e9abbaa 100644
--- a/lib.h
+++ b/lib.h
@@ -143,6 +143,37 @@ extern PRINTF_LIKE(2, 3) NORETURN
 	 * exit with status code 2.
 	 */
 
+/*----- Resizing vectors --------------------------------------------------*/
+
+#define DEFVEC(vtype, etype)						\
+	typedef struct { etype *v; size_t n, sz; } vtype
+#define VEC_INIT { 0, 0, 0 }
+	/* Define VTYPE as a (structured) type for vectors holding elements
+	 * of ETYPE.
+	 *
+	 * A vector V has `V.n' elements, addressed as `V.v[0]' up to
+	 * `V.v[V.n - 1]'.
+	 */
+
+#define VEC_FREE(vv) do {						\
+  free((vv)->v); (vv)->v 0; (vv)->n = (vv)->sz = 0;			\
+} while (0)
+	/* Free the vector VV.  It's safe to free a vector multiple times. */
+
+#define VEC_PUSH(p, vv) do {						\
+  size_t _want;								\
+  if ((vv)->n >= (vv)->sz) {						\
+    (vv)->sz = (vv)->sz ? 2*(vv)->sz : 32;				\
+    _want = (vv)->sz*sizeof(*(vv)->v);					\
+    (vv)->v = realloc((vv)->v, _want);					\
+    if (!(vv)->v) bail("out of memory allocating %zu bytes", _want);	\
+  }									\
+  (p) = &(vv)->v[(vv)->n++];						\
+} while (0)
+	/* Add an initialized element to the end of vector VV, storing its
+	 * address in P.
+	 */
+
 /*----- Parsing utilities -------------------------------------------------*/
 
 #define PNF_JUNK 1u
@@ -160,6 +191,12 @@ extern long parse_int(const char **p_inout, unsigned f,
 
 /*----- System utilities --------------------------------------------------*/
 
+extern double tvdiff(const struct timeval *tv_lo,
+		     const struct timeval *tv_hi);
+	/* Return the (signed) difference from TV_LO to TV_HI, as a floating-
+	 * point number of seconds.
+	 */
+
 extern void sit(double t);
 	/* Do nothing for T seconds.  As implied by the type, T may be
 	 * fractional.
-- 
2.11.0