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Scan fixed-width integers in vcscanf (#424)

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When a format string like %2x is provided, the width parameter was read
correctly as 2, but it was not used when decoding the number from the
input string (ie instead of reading 2 characters from the input string,
vcscanf read all the characters).

This change uses the value of width within the number decoding loop to
read fixed number of digits correctly. if width is zero (not provided),
the default of width is set as bits.

Fixes #423
This commit is contained in:
Gautham 2022-06-27 09:57:07 +05:30 • committed by GitHub
parent 32eec7df4c
commit a6f65eea7c
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 11 additions and 1 deletions
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4
libc/fmt/vcscanf.c
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@ -177,9 +177,11 @@ int vcscanf(int callback(void *), int unget(int, void *), void *arg,
DecodeNumber: DecodeNumber:
if (c != -1) { if (c != -1) {
number = 0; number = 0;
width = !width ? bits : width;
do { do {
diglet = kBase36[(unsigned char)c]; diglet = kBase36[(unsigned char)c];
if (1 <= diglet && diglet <= base) { if (1 <= diglet && diglet <= base) {
width -= 1;
number *= base; number *= base;
number += diglet - 1; number += diglet - 1;
} else if (thousands && diglet == ',') { } else if (thousands && diglet == ',') {
@ -187,7 +189,7 @@ int vcscanf(int callback(void *), int unget(int, void *), void *arg,
} else { } else {
break; break;
} }
} while ((c = callback(arg)) != -1); } while ((c = callback(arg)) != -1 && width > 0);
if (!discard) { if (!discard) {
uint128_t bane = (uint128_t)1 << (bits - 1); uint128_t bane = (uint128_t)1 << (bits - 1);
if (!(number & ~((bane - 1) | (issigned ? 0 : bane))) || if (!(number & ~((bane - 1) | (issigned ? 0 : bane))) ||

8
test/libc/fmt/sscanf_test.c
View file

@ -141,3 +141,11 @@ TEST(sscanf, testDiscard_notIncludedInCount) {
ASSERT_EQ(1, sscanf("hello there", "%*s %8s", buf)); ASSERT_EQ(1, sscanf("hello there", "%*s %8s", buf));
EXPECT_STREQ("there", buf); EXPECT_STREQ("there", buf);
} }
TEST(sscanf, testFixedWidthFormat_Integer) {
int r, g, b;
ASSERT_EQ(3, sscanf("#321030", "#%2x%2b%2d", &r, &g, &b));
ASSERT_EQ(0x32, r);
ASSERT_EQ(2, g);
ASSERT_EQ(30, b);
}