Build option (disabled) to align included free ranges on hash boundaries.

Part of an effort to make delta images more precise. But the increased size
of the images means this probably isn't worth it. Revisit when I have more
time (ha, ha!)

clientside/os/imagezip/GNUmakefile.in

@@ -113,6 +113,7 @@ WITH_FAT	= @WINSUPPORT@
 
 # Note: requires WITH_CRYPTO
 WITH_HASH	= 1
+WITH_HASHALIGN	= 0
 
 include $(OBJDIR)/Makeconf
 
@@ -234,6 +235,9 @@ SUBDIRCFLAGS	+= -DHASHSTATS
 SUBDIRS		+= hashmap
 ZIPLIBS		+= hashmap/libhashmap.a
 LIBS		+= -lcrypto $(PTHREADLIBS)
+ifeq ($(WITH_HASHALIGN),1)
+CFLAGS		+= -DWITH_HASHALIGN
+endif
 endif
 
 ifeq ($(WITH_RANGEMAP),1)

clientside/os/imagezip/imagezip.c

@@ -62,6 +62,9 @@
 #include "range.h"
 #ifdef WITH_HASH
 #include "hashmap/hashmap.h"
+#ifdef WITH_HASHALIGN
+#include "imagehash.h"
+#endif
 #endif
 
 /*
@@ -475,6 +478,12 @@ main(int argc, char *argv[])
 			compat = COMPRESSED_V3;
 			break;
 		case 'F':
+#ifdef WITH_HASHALIGN
+			if (strcmp(optarg, "ha") == 0) {
+				frangesize = -1;
+				break;
+			}
+#endif
 			frangesize = atoi(optarg);
 			if (frangesize < 0)
 				usage();
@@ -1546,7 +1555,66 @@ mergeskips(int verbose)
 		prevp = &skips;
 		while (*prevp) {
 			prange = *prevp;
+#ifdef WITH_HASHALIGN
+			/*
+			 * Free ranges should line up with hash ranges
+			 */
+			if (frangesize < 0) {
+				unsigned int hbsize, toff, tsize;
+				int didit = 0;
+
+				hbsize = bytestosec(HASHBLK_SIZE); /* XXX */
+				toff = prange->start % hbsize;
+				if (prange->size < hbsize ||
+				    (toff &&
+				     prange->size < (hbsize - toff) + hbsize))
+					goto dropall;
+
+				if (toff) {
+					tsize = hbsize - toff;
+					toff = prange->start;
+					
+					if (zerofrange)
+						addfixupfunc(zerofixup,
+							     sectobytes(toff),
+							     0,
+							     sectobytes(tsize),
+							     NULL, 0,
+							     RELOC_NONE);
+
+					prange->start += tsize;
+					prange->size -= tsize;
+					total += tsize;
+					didit++;
+				}
+				tsize = prange->size % hbsize;
+				if (tsize) {
+					toff = prange->start + prange->size
+						- tsize;
+					if (zerofrange)
+						addfixupfunc(zerofixup,
+							     sectobytes(toff),
+							     0,
+							     sectobytes(tsize),
+							     NULL, 0,
+							     RELOC_NONE);
+
+					prange->size -= tsize;
+					total += tsize;
+					didit++;
+				}
+				if (didit)
+					culled++;
+				assert(prange->size >= hbsize);
+				assert((prange->start % hbsize) == 0);
+				assert((prange->size % hbsize) == 0);
+				prevp = &prange->next;
+			} else
+#endif
 			if (prange->size < (uint32_t)frangesize) {
+#ifdef WITH_HASHALIGN
+			dropall:
+#endif
 				if (debug > 2)
 					fprintf(stderr,
 						"dropping range [%u-%u]\n",