t/helper: improve "genrandom" test helper

The `test-tool genrandom` test helper can be used to generate random
data, either as an infinite stream or with a specified number of bytes.
The way we handle parsing the number of bytes is lacking though:

  - We don't have good error handling, so if the caller for example uses
    `test-tool genrandom 200xyz` then we'll end up generating 200 bytes
    of random data successfully.

  - Many callers want to generate e.g. 1 kilobyte or megabyte of data,
    but they have to either use unwieldy numbers like 1048576, or they
    have to precompute them.

Fix both of these issues by using `git_parse_ulong()` to parse the
argument. This function has better error handling, and it knows to
handle unit suffixes.

Adapt a couple of our tests to use suffixes instead of manual
computations.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/t/helper/test-genrandom.c b/t/helper/test-genrandom.c
index 51b67f2f87..d681961abb 100644
--- a/t/helper/test-genrandom.c
+++ b/t/helper/test-genrandom.c
@@ -6,6 +6,7 @@
 
 #include "test-tool.h"
 #include "git-compat-util.h"
+#include "parse.h"
 
 int cmd__genrandom(int argc, const char **argv)
 {
@@ -22,7 +23,9 @@ int cmd__genrandom(int argc, const char **argv)
 		next = next * 11 + *c;
 	} while (*c++);
 
-	count = (argc == 3) ? strtoul(argv[2], NULL, 0) : ULONG_MAX;
+	count = ULONG_MAX;
+	if (argc == 3 && !git_parse_ulong(argv[2], &count))
+		return error_errno("cannot parse argument '%s'", argv[2]);
 
 	while (count--) {
 		next = next * 1103515245 + 12345;