[Tarantool-patches] [PATCH 2/2] decimal: introduce strtodec function

[Chris Sosnin <k.sosnin@tarantool.org>]

The behavior is similar with other strto* functions: parse the valid
beginning of the string and optionally store the pointer to the first
invalid character.

Needed for tarantool/tarantool#4415
---
 src/lib/core/decimal.c   | 14 +++++++++++++-
 src/lib/core/decimal.h   | 15 +++++++++++++++
 test/unit/decimal.c      | 20 +++++++++++++++++++-
 test/unit/decimal.result | 18 +++++++++++++++++-
 4 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/src/lib/core/decimal.c b/src/lib/core/decimal.c
index 019c68338..e762266c5 100644
--- a/src/lib/core/decimal.c
+++ b/src/lib/core/decimal.c
@@ -112,7 +112,19 @@ decimal_zero(decimal_t *dec)
 decimal_t *
 decimal_from_string(decimal_t *dec, const char *str)
 {
-	decNumberFromString(dec, str, &decimal_context);
+	const char *end = decNumberFromString(dec, str, &decimal_context);
+	if (*end != '\0') {
+		decContextZeroStatus(&decimal_context);
+		return NULL;
+	}
+	return decimal_check_status(dec, &decimal_context);
+}
+
+decimal_t *
+strtodec(decimal_t *dec, const char *str, const char **endptr) {
+	const char *end = decNumberFromString(dec, str, &decimal_context);
+	if (endptr != NULL)
+		*endptr = end;
 	return decimal_check_status(dec, &decimal_context);
 }
 
diff --git a/src/lib/core/decimal.h b/src/lib/core/decimal.h
index e276344d2..992fbd267 100644
--- a/src/lib/core/decimal.h
+++ b/src/lib/core/decimal.h
@@ -77,6 +77,21 @@ decimal_zero(decimal_t *dec);
 decimal_t *
 decimal_from_string(decimal_t *dec, const char *str);
 
+/**
+ * Initialize a decimal with a value from the valid beginning
+ * of the string.
+ * If \a endptr is not NULL, store the address of the first
+ * invalid character in *endptr.
+ *
+ * If the number is less, than 10^DECIMAL_MAX_DIGITS,
+ * but has excess digits in fractional part, it will be rounded.
+ *
+ * @return NULL if string is invalid or
+ * the number is too big (>= 10^DECIMAL_MAX_DIGITS)
+ */
+decimal_t *
+strtodec(decimal_t *dec, const char *str, const char **endptr);
+
 /**
  * Initialize a decimal from double.
  *
diff --git a/test/unit/decimal.c b/test/unit/decimal.c
index 179723d02..cf74de313 100644
--- a/test/unit/decimal.c
+++ b/test/unit/decimal.c
@@ -73,6 +73,15 @@
 	is(decimal_##op(&b, &a), NULL, "decimal_"#op"("#stra") - error on wrong operands.");\
 })
 
+#define test_strtodec(str, end, expect) ({\
+	decimal_t dec;\
+	const char *endptr;\
+	is(strtodec(&dec, str, &endptr), expect(&dec), "strtodec("#str") "\
+							#expect);\
+	is(*endptr, end, "strtodec("#str") - expected end of valid string at "\
+			  #end);\
+})
+
 char buf[32];
 
 #define test_mpdec(str) ({\
@@ -317,7 +326,7 @@ test_mp_print(void)
 int
 main(void)
 {
-	plan(282);
+	plan(298);
 
 	dectest(314, 271, uint64, uint64_t);
 	dectest(65535, 23456, uint64, uint64_t);
@@ -384,5 +393,14 @@ main(void)
 	test_mp_decimal();
 	test_mp_print();
 
+	test_strtodec("15.e", 'e', success);
+	test_strtodec("15.e+", 'e', success);
+	test_strtodec(".0e-1", '\0', success);
+	test_strtodec("1.1003 2.2", ' ', success);
+	test_strtodec("cCC", 'c', failure);
+	test_strtodec(".e--", '.', failure);
+	test_strtodec("NaN", 'N', failure);
+	test_strtodec("inf", 'i', failure);
+
 	return check_plan();
 }
diff --git a/test/unit/decimal.result b/test/unit/decimal.result
index f11396df3..8be8ea122 100644
--- a/test/unit/decimal.result
+++ b/test/unit/decimal.result
@@ -1,4 +1,4 @@
-1..282
+1..298
 ok 1 - decimal(314)
 ok 2 - decimal(271)
 ok 3 - decimal(314) + decimal(271)
@@ -707,3 +707,19 @@ ok 281 - subtests
     ok 5 - correct mp_fprint result
 	*** test_mp_print: done ***
 ok 282 - subtests
+ok 283 - strtodec("15.e") success
+ok 284 - strtodec("15.e") - expected end of valid string at 'e'
+ok 285 - strtodec("15.e+") success
+ok 286 - strtodec("15.e+") - expected end of valid string at 'e'
+ok 287 - strtodec(".0e-1") success
+ok 288 - strtodec(".0e-1") - expected end of valid string at '\0'
+ok 289 - strtodec("1.1003 2.2") success
+ok 290 - strtodec("1.1003 2.2") - expected end of valid string at ' '
+ok 291 - strtodec("cCC") failure
+ok 292 - strtodec("cCC") - expected end of valid string at 'c'
+ok 293 - strtodec(".e--") failure
+ok 294 - strtodec(".e--") - expected end of valid string at '.'
+ok 295 - strtodec("NaN") failure
+ok 296 - strtodec("NaN") - expected end of valid string at 'N'
+ok 297 - strtodec("inf") failure
+ok 298 - strtodec("inf") - expected end of valid string at 'i'
-- 
2.21.1 (Apple Git-122.3)