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Narrows template ascii routines to prevent a possible signed overflow in generic code. (#5232)

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This commit is contained in:
Vladimir Glavnyy
2019-03-12 00:26:28 +07:00
committed by Wouter van Oortmerssen
parent 73a648b685
commit 407fb5d537
2 changed files with 10 additions and 10 deletions
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16
include/flatbuffers/util.h
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@@ -35,19 +35,19 @@ namespace flatbuffers {
// @locale-independent functions for ASCII characters set. // @locale-independent functions for ASCII characters set.
// Check that integer scalar is in closed range: (a <= x <= b) // Fast checking that character lies in closed range: [a <= x <= b]
// using one compare (conditional branch) operator. // using one compare (conditional branch) operator.
template<typename T> inline bool check_in_range(T x, T a, T b) { inline bool check_ascii_range(char x, char a, char b) {
FLATBUFFERS_ASSERT(a <= b);
// (Hacker's Delight): `a <= x <= b` <=> `(x-a) <={u} (b-a)`. // (Hacker's Delight): `a <= x <= b` <=> `(x-a) <={u} (b-a)`.
FLATBUFFERS_ASSERT(a <= b); // static_assert only if 'a' & 'b' templated // The x, a, b will be promoted to int and subtracted without overflow.
typedef typename flatbuffers::make_unsigned<T>::type U; return static_cast<unsigned int>(x - a) <= static_cast<unsigned int>(b - a);
return (static_cast<U>(x - a) <= static_cast<U>(b - a));
} }
// Case-insensitive isalpha // Case-insensitive isalpha
inline bool is_alpha(char c) { inline bool is_alpha(char c) {
// ASCII only: alpha to upper case => reset bit 0x20 (~0x20 = 0xDF). // ASCII only: alpha to upper case => reset bit 0x20 (~0x20 = 0xDF).
return check_in_range(c & 0xDF, 'a' & 0xDF, 'z' & 0xDF); return check_ascii_range(c & 0xDF, 'a' & 0xDF, 'z' & 0xDF);
} }
// Check (case-insensitive) that `c` is equal to alpha. // Check (case-insensitive) that `c` is equal to alpha.
@@ -62,11 +62,11 @@ inline bool is_alpha_char(char c, char alpha) {
// functions that are not affected by the currently installed C locale. although // functions that are not affected by the currently installed C locale. although
// some implementations (e.g. Microsoft in 1252 codepage) may classify // some implementations (e.g. Microsoft in 1252 codepage) may classify
// additional single-byte characters as digits. // additional single-byte characters as digits.
inline bool is_digit(char c) { return check_in_range(c, '0', '9'); } inline bool is_digit(char c) { return check_ascii_range(c, '0', '9'); }
inline bool is_xdigit(char c) { inline bool is_xdigit(char c) {
// Replace by look-up table. // Replace by look-up table.
return is_digit(c) || check_in_range(c & 0xDF, 'a' & 0xDF, 'f' & 0xDF); return is_digit(c) || check_ascii_range(c & 0xDF, 'a' & 0xDF, 'f' & 0xDF);
} }
// Case-insensitive isalnum // Case-insensitive isalnum

4
src/idl_parser.cpp
View File

@@ -374,7 +374,7 @@ CheckedError Parser::Next() {
"illegal Unicode sequence (unpaired high surrogate)"); "illegal Unicode sequence (unpaired high surrogate)");
} }
// reset if non-printable // reset if non-printable
attr_is_trivial_ascii_string_ &= check_in_range(*cursor_, ' ', '~'); attr_is_trivial_ascii_string_ &= check_ascii_range(*cursor_, ' ', '~');
attribute_ += *cursor_++; attribute_ += *cursor_++;
} }
@@ -476,7 +476,7 @@ CheckedError Parser::Next() {
} }
std::string ch; std::string ch;
ch = c; ch = c;
if (false == check_in_range(c, ' ', '~')) ch = "code: " + NumToString(c); if (false == check_ascii_range(c, ' ', '~')) ch = "code: " + NumToString(c);
return Error("illegal character: " + ch); return Error("illegal character: " + ch);
} }
} }