49 static inline juint reverse_int(juint bits); // to trim trailing float 0's
50
51 public:
52 CompressedStream(u_char* buffer, int position = 0) {
53 _buffer = buffer;
54 _position = position;
55 }
56
57 u_char* buffer() const { return _buffer; }
58
59 // Positioning
60 int position() const { return _position; }
61 void set_position(int position) { _position = position; }
62 };
63
64
65 class CompressedReadStream : public CompressedStream {
66 private:
67 inline u_char read() { return _buffer[_position++]; }
68
69 jint read_int_mb(jint b0); // UNSIGNED5 coding, 2-5 byte cases
70
71 public:
72 CompressedReadStream(u_char* buffer, int position = 0)
73 : CompressedStream(buffer, position) {}
74
75 jboolean read_bool() { return (jboolean) read(); }
76 jbyte read_byte() { return (jbyte ) read(); }
77 jchar read_char() { return (jchar ) read_int(); }
78 jshort read_short() { return (jshort ) read_signed_int(); }
79 jint read_int() { jint b0 = read();
80 if (b0 < L) return b0;
81 else return read_int_mb(b0);
82 }
83 jint read_signed_int();
84 jfloat read_float(); // jfloat_cast(reverse_int(read_int()))
85 jdouble read_double(); // jdouble_cast(2*reverse_int(read_int))
86 jlong read_long(); // jlong_from(2*read_signed_int())
87 };
88
89
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49 static inline juint reverse_int(juint bits); // to trim trailing float 0's
50
51 public:
52 CompressedStream(u_char* buffer, int position = 0) {
53 _buffer = buffer;
54 _position = position;
55 }
56
57 u_char* buffer() const { return _buffer; }
58
59 // Positioning
60 int position() const { return _position; }
61 void set_position(int position) { _position = position; }
62 };
63
64
65 class CompressedReadStream : public CompressedStream {
66 private:
67 inline u_char read() { return _buffer[_position++]; }
68
69 // This encoding, called UNSIGNED5, is taken from J2SE Pack200.
70 // It assumes that most values have lots of leading zeroes.
71 // Very small values, in the range [0..191], code in one byte.
72 // Any 32-bit value (including negatives) can be coded, in
73 // up to five bytes. The grammar is:
74 // low_byte = [0..191]
75 // high_byte = [192..255]
76 // any_byte = low_byte | high_byte
77 // coding = low_byte
78 // | high_byte low_byte
79 // | high_byte high_byte low_byte
80 // | high_byte high_byte high_byte low_byte
81 // | high_byte high_byte high_byte high_byte any_byte
82 // Each high_byte contributes six bits of payload.
83 // The encoding is one-to-one (except for integer overflow)
84 // and easy to parse and unparse.
85
86 jint read_int_mb(jint b0) {
87 int pos = position() - 1;
88 u_char* buf = buffer() + pos;
89 assert(buf[0] == b0 && b0 >= L, "correctly called");
90 jint sum = b0;
91 // must collect more bytes: b[1]...b[4]
92 int lg_H_i = lg_H;
93 for (int i = 0; ; ) {
94 jint b_i = buf[++i]; // b_i = read(); ++i;
95 sum += b_i << lg_H_i; // sum += b[i]*(64**i)
96 if (b_i < L || i == MAX_i) {
97 set_position(pos+i+1);
98 return sum;
99 }
100 lg_H_i += lg_H;
101 }
102 }
103
104 public:
105 CompressedReadStream(u_char* buffer, int position = 0)
106 : CompressedStream(buffer, position) {}
107
108 jboolean read_bool() { return (jboolean) read(); }
109 jbyte read_byte() { return (jbyte ) read(); }
110 jchar read_char() { return (jchar ) read_int(); }
111 jshort read_short() { return (jshort ) read_signed_int(); }
112 jint read_int() { jint b0 = read();
113 if (b0 < L) return b0;
114 else return read_int_mb(b0);
115 }
116 jint read_signed_int();
117 jfloat read_float(); // jfloat_cast(reverse_int(read_int()))
118 jdouble read_double(); // jdouble_cast(2*reverse_int(read_int))
119 jlong read_long(); // jlong_from(2*read_signed_int())
120 };
121
122
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