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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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4
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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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0
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34
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4
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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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0
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39
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4
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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);
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49 return b[ptr++];
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50 }
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51
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52 public final int readS16() throws Exception {
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53 check(2);
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54 int b0 = b[ptr++];
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55 int b1 = b[ptr++] & 0xff;
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56 return b0 << 8 | b1;
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57 }
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58
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59 public final int readS32() throws Exception {
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60 check(4);
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61 int b0 = b[ptr++];
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62 int b1 = b[ptr++] & 0xff;
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63 int b2 = b[ptr++] & 0xff;
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64 int b3 = b[ptr++] & 0xff;
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65 return b0 << 24 | b1 << 16 | b2 << 8 | b3;
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66 }
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67
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68 public final int readU8() throws Exception {
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69 return readS8() & 0xff;
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70 }
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71
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72 public final int readU16() throws Exception {
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73 return readS16() & 0xffff;
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74 }
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75
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76 public final int readU32() throws Exception {
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77 return readS32() & 0xffffffff;
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78 }
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79
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80 // readString() reads a string - a U32 length followed by the data.
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81
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82 public final String readString() throws Exception {
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83 int len = readU32();
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84 if (len > maxStringLength)
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85 throw new Exception("InStream max string length exceeded");
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0
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86
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87 char[] str = new char[len];
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88 int i = 0;
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89 while (i < len) {
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90 int j = i + check(1, len - i);
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91 while (i < j) {
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92 str[i++] = (char) b[ptr++];
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93 }
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94 }
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95
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96 return new String(str);
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97 }
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98
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99 // maxStringLength protects against allocating a huge buffer. Set it
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100 // higher if you need longer strings.
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101
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102 public static int maxStringLength = 65535;
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103
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104 public final void skip(int bytes) throws Exception {
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105 while (bytes > 0) {
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106 int n = check(1, bytes);
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107 ptr += n;
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108 bytes -= n;
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109 }
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110 }
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111
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112 // readBytes() reads an exact number of bytes into an array at an offset.
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113
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114 public void readBytes(byte[] data, int offset, int length) throws Exception {
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115 int offsetEnd = offset + length;
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116 while (offset < offsetEnd) {
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117 int n = check(1, offsetEnd - offset);
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118 System.arraycopy(b, ptr, data, offset, n);
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119 ptr += n;
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120 offset += n;
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121 }
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122 }
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123
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124 // readOpaqueN() reads a quantity "without byte-swapping". Because java has
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125 // no byte-ordering, we just use big-endian.
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126
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127 public final int readOpaque8() throws Exception {
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128 return readU8();
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129 }
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130
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131 public final int readOpaque16() throws Exception {
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132 return readU16();
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133 }
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134
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135 public final int readOpaque32() throws Exception {
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136 return readU32();
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137 }
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138
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139 public final int readOpaque24A() throws Exception {
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140 check(3);
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141 int b0 = b[ptr++];
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142 int b1 = b[ptr++];
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143 int b2 = b[ptr++];
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144 return b0 << 24 | b1 << 16 | b2 << 8;
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145 }
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146
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147 public final int readOpaque24B() throws Exception {
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148 check(3);
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149 int b0 = b[ptr++];
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150 int b1 = b[ptr++];
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151 int b2 = b[ptr++];
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152 return b0 << 16 | b1 << 8 | b2;
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153 }
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154
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155 // pos() returns the position in the stream.
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156
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157 abstract public int pos();
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158
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159 // bytesAvailable() returns true if at least one byte can be read from the
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160 // stream without blocking. i.e. if false is returned then readU8() would
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161 // block.
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162
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163 public boolean bytesAvailable() {
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164 return end != ptr;
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165 }
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166
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167 // getbuf(), getptr(), getend() and setptr() are "dirty" methods which allow
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168 // you to manipulate the buffer directly. This is useful for a stream which
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169 // is a wrapper around an underlying stream.
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170
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171 public final byte[] getbuf() {
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172 return b;
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173 }
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174
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175 public final int getptr() {
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176 return ptr;
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177 }
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178
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179 public final int getend() {
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180 return end;
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181 }
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182
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183 public final void setptr(int p) {
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184 ptr = p;
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185 }
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186
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187 // overrun() is implemented by a derived class to cope with buffer overrun.
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188 // It ensures there are at least itemSize bytes of buffer data. Returns
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189 // the number of items in the buffer (up to a maximum of nItems). itemSize
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190 // is supposed to be "small" (a few bytes).
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191
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192 abstract protected int overrun(int itemSize, int nItems) throws Exception;
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193
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194 protected InStream() {
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195 }
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196
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197 protected byte[] b;
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198 protected int ptr;
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199 protected int end;
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200 }
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