8000 String relational operators · szeder/ArduinoCore-API@893bcc5 · GitHub
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BillyDonahuefacchinm
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String relational operators
The String class has an incomplete set of relational operators with `const char*`. The 6 operators `==`,`!=`,`<`,`>`,`<=`,`>=` must be defined between String and String, but also between String and `const char*`. The motivation is to treat left and right operands symmetrically. str == "hello" works, but swapping arguments to "hello" == str doesn't, which is a potential user surprise. As String is implicitly convertible from `const char*`, but this incurs a "strdup". So it also makes sense to provide relational operators directly with const char* to avoid the expensive promotion of const char* to temporary String, just to do a string value comparison. Resolves: #7139
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lines changed

2 files changed

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lines changed

‎api/String.cpp

Lines changed: 10 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -443,6 +443,16 @@ int String::compareTo(const String &s) const
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return strcmp(buffer, s.buffer);
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}
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int String::compareTo(const char *cstr) const
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{
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if (!buffer || !cstr) {
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if (cstr && !*cstr) return 0 - *(unsigned char *)cstr;
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if (buffer && len > 0) return *(unsigned char *)buffer;
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return 0;
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}
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return strcmp(buffer, cstr);
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}
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unsigned char String::equals(const String &s2) const
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{
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return (len == s2.len && compareTo(s2) == 0);
@@ -455,26 +465,6 @@ unsigned char String::equals(const char *cstr) const
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return strcmp(buffer, cstr) == 0;
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}
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unsigned char String::operator<(const String &rhs) const
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{
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return compareTo(rhs) < 0;
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}
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unsigned char String::operator>(const String &rhs) const
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{
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return compareTo(rhs) > 0;
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}
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unsigned char String::operator<=(const String &rhs) const
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{
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return compareTo(rhs) <= 0;
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}
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unsigned char String::operator>=(const String &rhs) const
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{
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return compareTo(rhs) >= 0;
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}
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unsigned char String::equalsIgnoreCase( const String &s2 ) const
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{
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if (this == &s2) return 1;

‎api/String.h

Lines changed: 22 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -141,16 +141,30 @@ class String
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// comparison (only works w/ Strings and "strings")
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operator StringIfHelperType() const { return buffer ? &String::StringIfHelper : 0; }
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int compareTo(const String &s) const;
144+
int compareTo(const char *cstr) const;
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unsigned char equals(const String &s) const;
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unsigned char equals(const char *cstr) const;
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unsigned char operator == (const String &rhs) const {return equals(rhs);}
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unsigned char operator == (const char *cstr) const {return equals(cstr);}
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unsigned char operator != (const String &rhs) const {return !equals(rhs);}
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unsigned char operator != (const char *cstr) const {return !equals(cstr);}
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unsigned char operator < (const String &rhs) const;
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unsigned char operator > (const String &rhs) const;
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unsigned char operator <= (const String &rhs) const;
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unsigned char operator >= (const String &rhs) const;
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friend unsigned char operator == (const String &a, const String &b) { return a.equals(b); }
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friend unsigned char operator == (const String &a, const char *b) { return a.equals(b); }
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friend unsigned char operator == (const char *a, const String &b) { return b == a; }
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friend unsigned char operator < (const String &a, const String &b) { return a.compareTo(b) < 0; }
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friend unsigned char operator < (const String &a, const char *b) { return a.compareTo(b) < 0; }
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friend unsigned char operator < (const char *a, const String &b) { return b.compareTo(a) > 0; }
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friend unsigned char operator != (const String &a, const String &b) { return !(a == b); }
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friend unsigned char operator != (const String &a, const char *b) { return !(a == b); }
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friend unsigned char operator != (const char *a, const String &b) { return !(a == b); }
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friend unsigned char operator > (const String &a, const String &b) { return b < a; }
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friend unsigned char operator > (const String &a, const char *b) { return b < a; }
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friend unsigned char operator > (const char *a, const String &b) { return b < a; }
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friend unsigned char operator <= (const String &a, const String &b) { return !(b < a); }
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friend unsigned char operator <= (const String &a, const char *b) { return !(b < a); }
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friend unsigned char operator <= (const char *a, const String &b) { return !(b < a); }
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friend unsigned char operator >= (const String &a, const String &b) { return !(a < b); }
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friend unsigned char operator >= (const String &a, const char *b) { return !(a < b); }
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friend unsigned char operator >= (const char *a, const String &b) { return !(a < b); }
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unsigned char equalsIgnoreCase(const String &s) const;
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unsigned char startsWith( const String &prefix) const;
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unsigned char startsWith(const String &prefix, unsigned int offset) const;

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