more accurate error message

src/secret.c

@@ -347,21 +347,21 @@ SEXP secretbase_sha3_file(SEXP x, SEXP bits, SEXP convert) {
   const int size = validate_bitlength(bits);
   const size_t outlen = (size_t) (size / 8);
   unsigned char output[outlen];
-  unsigned char buf[4096];
+  unsigned char buf[SB_BUF_SIZE];
   size_t cur;
 
   mbedtls_sha3_id id = id_from_size(size);
   mbedtls_sha3_context ctx;
   mbedtls_sha3_init(&ctx);
   mbedtls_sha3_starts(&ctx, id);
 
-  FILE *f = fopen(file, "rb");
-  if (f == NULL)
-    Rf_error("file not found");
-  while ((cur = fread(buf, 1, sizeof(buf), f))) {
+  FILE *fp = fopen(file, "rb");
+  if (fp == NULL)
+    Rf_error("file not found or accessible");
+  while ((cur = fread(buf, 1, sizeof(buf), fp))) {
     mbedtls_sha3_update(&ctx, buf, cur);
   }
-  fclose(f);
+  fclose(fp);
 
   mbedtls_sha3_finish(&ctx, output, outlen);
 

src/secret.h

@@ -28,6 +28,7 @@
 
 #define SB_R_SERIAL_VER 3
 #define SB_SERIAL_HEADERS 6
+#define SB_BUF_SIZE 4096
 
 typedef enum {
   MBEDTLS_SHA3_NONE = 0,

tests/tests.R

@@ -31,10 +31,10 @@ test_error(sha3("secret base", bits = 0), "'bits' must be between 8 and 2^24")
 test_error(sha3("secret base", bits = -1), "'bits' must be between 8 and 2^24")
 test_error(sha3("secret base", bits = 2^24 + 1), "'bits' must be between 8 and 2^24")
 # File interface tests:
-hash_func <- function(file = tempfile()) {
-  cat("secret base", file = file)
+hash_func <- function(file, string) {
   on.exit(unlink(file))
+  cat(string, file = file)
   sha3sum(file)
 }
-test_equal(hash_func(), "a721d57570e7ce366adee2fccbe9770723c6e3622549c31c7cab9dbb4a795520")
-test_error(sha3sum(""), "file not found")
+test_equal(hash_func(tempfile(), "secret base"), "a721d57570e7ce366adee2fccbe9770723c6e3622549c31c7cab9dbb4a795520")
+test_error(hash_func("", ""), "file not found or accessible")