ClickHouse/dbms/src/Functions/likePatternToRegexp.h

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#pragma once
#include <Core/Types.h>
namespace DB
{
2017-05-13 22:19:04 +00:00
/// Transforms the LIKE expression into regexp re2. For example, abc%def -> ^abc.*def$
inline String likePatternToRegexp(const String & pattern)
{
String res;
res.reserve(pattern.size() * 2);
const char * pos = pattern.data();
const char * end = pos + pattern.size();
if (pos < end && *pos == '%')
++pos;
else
res = "^";
while (pos < end)
{
switch (*pos)
{
case '^': case '$': case '.': case '[': case '|': case '(': case ')': case '?': case '*': case '+': case '{':
res += '\\';
res += *pos;
break;
case '%':
if (pos + 1 != end)
res += ".*";
else
return res;
break;
case '_':
res += ".";
break;
case '\\':
++pos;
if (pos == end)
res += "\\\\";
else
{
if (*pos == '%' || *pos == '_')
res += *pos;
else
{
res += '\\';
res += *pos;
}
}
break;
default:
res += *pos;
break;
}
++pos;
}
res += '$';
return res;
}
}