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1 /* Copyright (C) 2002-2005 RealVNC Ltd. All Rights Reserved.
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2 *
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3 * This is free software; you can redistribute it and/or modify
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4 * it under the terms of the GNU General Public License as published by
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5 * the Free Software Foundation; either version 2 of the License, or
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6 * (at your option) any later version.
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7 *
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8 * This software is distributed in the hope that it will be useful,
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9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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11 * GNU General Public License for more details.
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12 *
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13 * You should have received a copy of the GNU General Public License
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14 * along with this software; if not, write to the Free Software
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15 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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16 * USA.
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17 */
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18
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19 //
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20 // rdr::InStream marshalls data from a buffer stored in RDR (RFB Data
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21 // Representation).
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22 //
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23
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24 abstract public class InStream {
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25
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26 // check() ensures there is buffer data for at least one item of size
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27 // itemSize bytes. Returns the number of items in the buffer (up to a
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28 // maximum of nItems).
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29
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30 public final int check(int itemSize, int nItems) throws Exception {
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31 if (ptr + itemSize * nItems > end) {
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32 if (ptr + itemSize > end)
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33 return overrun(itemSize, nItems);
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34
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35 nItems = (end - ptr) / itemSize;
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36 }
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37 return nItems;
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38 }
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39
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40 public final void check(int itemSize) throws Exception {
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41 if (ptr + itemSize > end)
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42 overrun(itemSize, 1);
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43 }
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44
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45 // readU/SN() methods read unsigned and signed N-bit integers.
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46
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47 public final int readS8() throws Exception {
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48 check(1); return b[ptr++];
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49 }
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50
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51 public final int readS16() throws Exception {
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52 check(2); int b0 = b[ptr++];
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53 int b1 = b[ptr++] & 0xff; return b0 << 8 | b1;
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54 }
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55
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56 public final int readS32() throws Exception {
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57 check(4); int b0 = b[ptr++];
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58 int b1 = b[ptr++] & 0xff;
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59 int b2 = b[ptr++] & 0xff;
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60 int b3 = b[ptr++] & 0xff;
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61 return b0 << 24 | b1 << 16 | b2 << 8 | b3;
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62 }
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63
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64 public final int readU8() throws Exception {
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65 return readS8() & 0xff;
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66 }
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67
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68 public final int readU16() throws Exception {
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69 return readS16() & 0xffff;
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70 }
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71
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72 public final int readU32() throws Exception {
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73 return readS32() & 0xffffffff;
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74 }
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75
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76 // readString() reads a string - a U32 length followed by the data.
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77
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78 public final String readString() throws Exception {
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79 int len = readU32();
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80 if (len > maxStringLength)
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81 throw new Exception("InStream max string length exceeded");
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82
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83 char[] str = new char[len];
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84 int i = 0;
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85 while (i < len) {
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86 int j = i + check(1, len - i);
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87 while (i < j) {
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88 str[i++] = (char)b[ptr++];
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89 }
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90 }
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91
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92 return new String(str);
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93 }
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94
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95 // maxStringLength protects against allocating a huge buffer. Set it
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96 // higher if you need longer strings.
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97
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98 public static int maxStringLength = 65535;
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99
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100 public final void skip(int bytes) throws Exception {
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101 while (bytes > 0) {
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102 int n = check(1, bytes);
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103 ptr += n;
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104 bytes -= n;
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105 }
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106 }
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107
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108 // readBytes() reads an exact number of bytes into an array at an offset.
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109
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110 public void readBytes(byte[] data, int offset, int length) throws Exception {
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111 int offsetEnd = offset + length;
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112 while (offset < offsetEnd) {
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113 int n = check(1, offsetEnd - offset);
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114 System.arraycopy(b, ptr, data, offset, n);
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115 ptr += n;
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116 offset += n;
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117 }
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118 }
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119
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120 // readOpaqueN() reads a quantity "without byte-swapping". Because java has
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121 // no byte-ordering, we just use big-endian.
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122
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123 public final int readOpaque8() throws Exception {
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124 return readU8();
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125 }
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126
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127 public final int readOpaque16() throws Exception {
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128 return readU16();
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129 }
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130
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131 public final int readOpaque32() throws Exception {
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132 return readU32();
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133 }
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134
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135 public final int readOpaque24A() throws Exception {
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136 check(3); int b0 = b[ptr++];
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137 int b1 = b[ptr++]; int b2 = b[ptr++];
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138 return b0 << 24 | b1 << 16 | b2 << 8;
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139 }
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140
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141 public final int readOpaque24B() throws Exception {
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142 check(3); int b0 = b[ptr++];
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143 int b1 = b[ptr++]; int b2 = b[ptr++];
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144 return b0 << 16 | b1 << 8 | b2;
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145 }
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146
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147 // pos() returns the position in the stream.
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148
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149 abstract public int pos();
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150
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151 // bytesAvailable() returns true if at least one byte can be read from the
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152 // stream without blocking. i.e. if false is returned then readU8() would
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153 // block.
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154
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155 public boolean bytesAvailable() { return end != ptr; }
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156
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157 // getbuf(), getptr(), getend() and setptr() are "dirty" methods which allow
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158 // you to manipulate the buffer directly. This is useful for a stream which
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159 // is a wrapper around an underlying stream.
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160
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161 public final byte[] getbuf() { return b; }
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162 public final int getptr() { return ptr; }
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163 public final int getend() { return end; }
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164 public final void setptr(int p) { ptr = p; }
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165
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166 // overrun() is implemented by a derived class to cope with buffer overrun.
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167 // It ensures there are at least itemSize bytes of buffer data. Returns
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168 // the number of items in the buffer (up to a maximum of nItems). itemSize
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169 // is supposed to be "small" (a few bytes).
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170
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171 abstract protected int overrun(int itemSize, int nItems) throws Exception;
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172
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173 protected InStream() {}
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174 protected byte[] b;
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175 protected int ptr;
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176 protected int end;
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177 }
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