Allow UseDelta option to specify a delta ratio

Rework the frontend and backend to allow passing a ratio value in for
UseDelta rather than having a hardcoded #define-d 0.7 value always used.
This is useful for those with fast connections, who would likely benefit
from tuning this ratio to lower values; it is also useful for general
testing purposes.

The libalpm API changes for this, but we do support the old config file
format with a no-value 'UseDelta' option; in this case we simply use the
old default of 0.7.

We clamp the ratio values to a sane range between 0.0 and 2.0, allowing
ratios above 1.0 for testing purposes.

Signed-off-by: Dan McGee <dan@archlinux.org>

6 files changed, 15 insertions, 13 deletions

diff --git a/lib/libalpm/alpm.h b/lib/libalpm/alpm.h
index 95c817ea..9ffdebc5 100644
--- a/lib/libalpm/alpm.h
+++ b/lib/libalpm/alpm.h
@@ -535,8 +535,8 @@ const char *alpm_option_get_arch(alpm_handle_t *handle);
 /** Sets the targeted architecture. */
 int alpm_option_set_arch(alpm_handle_t *handle, const char *arch);
 
-int alpm_option_get_usedelta(alpm_handle_t *handle);
-int alpm_option_set_usedelta(alpm_handle_t *handle, int usedelta);
+double alpm_option_get_deltaratio(alpm_handle_t *handle);
+int alpm_option_set_deltaratio(alpm_handle_t *handle, double ratio);
 
 int alpm_option_get_checkspace(alpm_handle_t *handle);
 int alpm_option_set_checkspace(alpm_handle_t *handle, int checkspace);
diff --git a/lib/libalpm/delta.c b/lib/libalpm/delta.c
index 726f03c0..e3acc666 100644
--- a/lib/libalpm/delta.c
+++ b/lib/libalpm/delta.c
@@ -264,7 +264,8 @@ static alpm_list_t *find_unused(alpm_list_t *deltas, const char *to, off_t quota
 alpm_list_t SYMEXPORT *alpm_pkg_unused_deltas(alpm_pkg_t *pkg)
 {
 	ASSERT(pkg != NULL, return NULL);
-	return find_unused(pkg->deltas, pkg->filename, pkg->size * MAX_DELTA_RATIO);
+	return find_unused(pkg->deltas, pkg->filename,
+			pkg->size * pkg->handle->deltaratio);
 }
 
 /** @} */
diff --git a/lib/libalpm/delta.h b/lib/libalpm/delta.h
index 1173ddfe..37f208b0 100644
--- a/lib/libalpm/delta.h
+++ b/lib/libalpm/delta.h
@@ -30,9 +30,6 @@ alpm_delta_t *_alpm_delta_dup(const alpm_delta_t *delta);
 off_t _alpm_shortest_delta_path(alpm_handle_t *handle, alpm_list_t *deltas,
 		const char *to, alpm_list_t **path);
 
-/* max percent of package size to download deltas */
-#define MAX_DELTA_RATIO 0.7
-
 #endif /* _ALPM_DELTA_H */
 
 /* vim: set ts=2 sw=2 noet: */
diff --git a/lib/libalpm/handle.c b/lib/libalpm/handle.c
index 8e2e3c73..2187dca9 100644
--- a/lib/libalpm/handle.c
+++ b/lib/libalpm/handle.c
@@ -43,6 +43,7 @@ alpm_handle_t *_alpm_handle_new(void)
 	alpm_handle_t *handle;
 
 	CALLOC(handle, 1, sizeof(alpm_handle_t), return NULL);
+	handle->deltaratio = 0.0;
 
 	return handle;
 }
@@ -252,10 +253,10 @@ const char SYMEXPORT *alpm_option_get_arch(alpm_handle_t *handle)
 	return handle->arch;
 }
 
-int SYMEXPORT alpm_option_get_usedelta(alpm_handle_t *handle)
+double SYMEXPORT alpm_option_get_deltaratio(alpm_handle_t *handle)
 {
 	CHECK_HANDLE(handle, return -1);
-	return handle->usedelta;
+	return handle->deltaratio;
 }
 
 int SYMEXPORT alpm_option_get_checkspace(alpm_handle_t *handle)
@@ -597,10 +598,13 @@ int SYMEXPORT alpm_option_set_arch(alpm_handle_t *handle, const char *arch)
 	return 0;
 }
 
-int SYMEXPORT alpm_option_set_usedelta(alpm_handle_t *handle, int usedelta)
+int SYMEXPORT alpm_option_set_deltaratio(alpm_handle_t *handle, double ratio)
 {
 	CHECK_HANDLE(handle, return -1);
-	handle->usedelta = usedelta;
+	if(ratio < 0.0 || ratio > 2.0) {
+		RET_ERR(handle, ALPM_ERR_WRONG_ARGS, -1);
+	}
+	handle->deltaratio = ratio;
 	return 0;
 }
 
diff --git a/lib/libalpm/handle.h b/lib/libalpm/handle.h
index a64c5c9e..a090ae42 100644
--- a/lib/libalpm/handle.h
+++ b/lib/libalpm/handle.h
@@ -88,8 +88,8 @@ struct __alpm_handle_t {
 
 	/* options */
 	char *arch;              /* Architecture of packages we should allow */
+	double deltaratio;       /* Download deltas if possible; a ratio value */
 	int usesyslog;           /* Use syslog instead of logfile? */ /* TODO move to frontend */
-	int usedelta;            /* Download deltas if possible */
 	int checkspace;          /* Check disk space before installing */
 	alpm_siglevel_t siglevel;   /* Default signature verification level */
 
diff --git a/lib/libalpm/sync.c b/lib/libalpm/sync.c
index 49a3f42d..6967b49b 100644
--- a/lib/libalpm/sync.c
+++ b/lib/libalpm/sync.c
@@ -318,13 +318,13 @@ static int compute_download_size(alpm_pkg_t *newpkg)
 
 		/* tell the caller that we have a partial */
 		ret = 1;
-	} else if(handle->usedelta) {
+	} else if(handle->deltaratio > 0.0) {
 		off_t dltsize;
 
 		dltsize = _alpm_shortest_delta_path(handle, newpkg->deltas,
 				newpkg->filename, &newpkg->delta_path);
 
-		if(newpkg->delta_path && (dltsize < newpkg->size * MAX_DELTA_RATIO)) {
+		if(newpkg->delta_path && (dltsize < newpkg->size * handle->deltaratio)) {
 			_alpm_log(handle, ALPM_LOG_DEBUG, "using delta size\n");
 			size = dltsize;
 		} else {