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分享unsigned long g=h&0Xf0000000L;//这是什么意思???
（著名的ELFhash算法）
int ELFhash(char *key)
{
unsigned long h=0;
while(*key)
{
h=(h<<4)+*key++;
unsigned long g=h&0Xf0000000L;
if(g)
h^=g>>24;
h&=~g;
}
return h%MOD;
}
...全文
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mirroatl187 2014-04-03
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unsigned long g=h&0Xf0000000L;
这句g的结果永远都是0吧？
turing-complete 2014-03-31
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代表这个整数是长整型。
赵4老师 2014-03-31
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C++ Integer Constants
Integer constants are constant data elements that have no fractional parts or exponents. They always begin with a digit. You can specify integer constants in decimal, octal, or hexadecimal form. They can specify signed or unsigned types and long or short types.
Syntax
integer-constant :
decimal-constant integer-suffixopt
octal-constant integer-suffixopt
hexadecimal-constant integer-suffixopt
'c-char-sequence'
decimal-constant :
nonzero-digit
decimal-constant digit
octal-constant :
0
octal-constant octal-digit
hexadecimal-constant :
0x hexadecimal-digit
0X hexadecimal-digit
hexadecimal-constant hexadecimal-digit
nonzero-digit : one of
1 2 3 4 5 6 7 8 9
octal-digit : one of
0 1 2 3 4 5 6 7
hexadecimal-digit : one of
0 1 2 3 4 5 6 7 8 9
a b c d e f
A B C D E F
integer-suffix :
unsigned-suffix long-suffixopt
long-suffix unsigned-suffixopt
unsigned-suffix : one of
u U
long-suffix : one of
l L
64-bit integer-suffix :
i64
To specify integer constants using octal or hexadecimal notation, use a prefix that denotes the base. To specify an integer constant of a given integral type, use a suffix that denotes the type.
To specify a decimal constant, begin the specification with a nonzero digit. For example:
int i = 157; // Decimal constant
int j = 0198; // Not a decimal number; erroneous octal constant
int k = 0365; // Leading zero specifies octal constant, not decimal
To specify an octal constant, begin the specification with 0, followed by a sequence of digits in the range 0 through 7. The digits 8 and 9 are errors in specifying an octal constant. For example:
int i = 0377; // Octal constant
int j = 0397; // Error: 9 is not an octal digit
To specify a hexadecimal constant, begin the specification with 0x or 0X (the case of the “x” does not matter), followed by a sequence of digits in the range 0 through 9 and a (or A) through f (or F). Hexadecimal digits a (or A) through f (or F) represent values in the range 10 through 15. For example:
int i = 0x3fff; // Hexadecimal constant
int j = 0X3FFF; // Equal to i
To specify an unsigned type, use either the u or U suffix. To specify a long type, use either the l or L suffix. For example:
unsigned uVal = 328u; // Unsigned value
long lVal = 0x7FFFFFL; // Long value specified
// as hex constant
unsigned long ulVal = 0776745ul; // Unsigned long value
赵4老师 2014-03-31
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//C++ Operators
// Operators specify an evaluation to be performed on one of the following:
// One operand (unary operator)
// Two operands (binary operator)
// Three operands (ternary operator)
// The C++ language includes all C operators and adds several new operators.
// Table 1.1 lists the operators available in Microsoft C++.
// Operators follow a strict precedence which defines the evaluation order of
//expressions containing these operators. Operators associate with either the
//expression on their left or the expression on their right; this is called
//“associativity.” Operators in the same group have equal precedence and are
//evaluated left to right in an expression unless explicitly forced by a pair of
//parentheses, ( ).
// Table 1.1 shows the precedence and associativity of C++ operators
// (from highest to lowest precedence).
//
//Table 1.1 C++ Operator Precedence and Associativity
// The highest precedence level is at the top of the table.
//+------------------+-----------------------------------------+---------------+
//| Operator | Name or Meaning | Associativity |
//+------------------+-----------------------------------------+---------------+
//| :: | Scope resolution | None |
//| :: | Global | None |
//| [ ] | Array subscript | Left to right |
//| ( ) | Function call | Left to right |
//| ( ) | Conversion | None |
//| . | Member selection (object) | Left to right |
//| -> | Member selection (pointer) | Left to right |
//| ++ | Postfix increment | None |
//| -- | Postfix decrement | None |
//| new | Allocate object | None |
//| delete | Deallocate object | None |
//| delete[ ] | Deallocate object | None |
//| ++ | Prefix increment | None |
//| -- | Prefix decrement | None |
//| * | Dereference | None |
//| & | Address-of | None |
//| + | Unary plus | None |
//| - | Arithmetic negation (unary) | None |
//| ! | Logical NOT | None |
//| ~ | Bitwise complement | None |
//| sizeof | Size of object | None |
//| sizeof ( ) | Size of type | None |
//| typeid( ) | type name | None |
//| (type) | Type cast (conversion) | Right to left |
//| const_cast | Type cast (conversion) | None |
//| dynamic_cast | Type cast (conversion) | None |
//| reinterpret_cast | Type cast (conversion) | None |
//| static_cast | Type cast (conversion) | None |
//| .* | Apply pointer to class member (objects) | Left to right |
//| ->* | Dereference pointer to class member | Left to right |
//| * | Multiplication | Left to right |
//| / | Division | Left to right |
//| % | Remainder (modulus) | Left to right |
//| + | Addition | Left to right |
//| - | Subtraction | Left to right |
//| << | Left shift | Left to right |
//| >> | Right shift | Left to right |
//| < | Less than | Left to right |
//| > | Greater than | Left to right |
//| <= | Less than or equal to | Left to right |
//| >= | Greater than or equal to | Left to right |
//| == | Equality | Left to right |
//| != | Inequality | Left to right |
//| & | Bitwise AND | Left to right |
//| ^ | Bitwise exclusive OR | Left to right |
//| | | Bitwise OR | Left to right |
//| && | Logical AND | Left to right |
//| || | Logical OR | Left to right |
//| e1?e2:e3 | Conditional | Right to left |
//| = | Assignment | Right to left |
//| *= | Multiplication assignment | Right to left |
//| /= | Division assignment | Right to left |
//| %= | Modulus assignment | Right to left |
//| += | Addition assignment | Right to left |
//| -= | Subtraction assignment | Right to left |
//| <<= | Left-shift assignment | Right to left |
//| >>= | Right-shift assignment | Right to left |
//| &= | Bitwise AND assignment | Right to left |
//| |= | Bitwise inclusive OR assignment | Right to left |
//| ^= | Bitwise exclusive OR assignment | Right to left |
//| , | Comma | Left to right |
//+------------------+-----------------------------------------+---------------+
Johnblx 2014-03-31
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单单这一句的话，是指，取h的高四位数据，其余位数取0，
derekrose 2014-03-30
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你是不懂上下文还是单单这一句
turing-complete 2014-03-30
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对于一个32位整数而言，只保留其高4位的数据，其余的置0.
mirroatl197 2014-03-30
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L代表啥意思???
PDD123 2014-03-30
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C++ 汇编 描述
& and 与运算
| or 或运算
^ xor 异或运算
~ not 非运算(求补)
PDD123 2014-03-30
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unsigned long g=h&0Xf0000000L;
与运算，每个二进制位都进行与运算。
这一句是保留h的最高的四个二进制位，其余都置为0，并把值保存在g中，h不变
