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1 //
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2 // File descriptors
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3 //
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4
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5 #include "types.h"
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6 #include "defs.h"
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7 #include "param.h"
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8 #include "fs.h"
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9 #include "file.h"
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10 #include "spinlock.h"
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32
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11 #include "proc.h"
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12
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52
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13 #define __ncode __code
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14 #
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15 struct devsw devsw[NDEV];
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27
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16 struct cbc_devsw cbc_devsw[NDEV];
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17
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18 struct {
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19 struct spinlock lock;
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20 struct file file[NFILE];
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21 } ftable;
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22
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23 void fileinit (void)
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24 {
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25 initlock(&ftable.lock, "ftable");
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26 }
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27
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28 // Allocate a file structure.
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29 struct file* filealloc (void)
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30 {
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31 struct file *f;
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32
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33 acquire(&ftable.lock);
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34
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35 for (f = ftable.file; f < ftable.file + NFILE; f++) {
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36 if (f->ref == 0) {
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37 f->ref = 1;
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38 release(&ftable.lock);
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39 return f;
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40 }
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41 }
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42
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43 release(&ftable.lock);
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44 return 0;
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45 }
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46
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47 // Increment ref count for file f.
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48 struct file* filedup (struct file *f)
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49 {
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50 acquire(&ftable.lock);
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51
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52 if (f->ref < 1) {
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53 panic("filedup");
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54 }
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55
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56 f->ref++;
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57 release(&ftable.lock);
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58 return f;
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59 }
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60
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61 // Close file f. (Decrement ref count, close when reaches 0.)
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62 void fileclose (struct file *f)
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63 {
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64 struct file ff;
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65
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66 acquire(&ftable.lock);
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67
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68 if (f->ref < 1) {
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69 panic("fileclose");
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70 }
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71
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72 if (--f->ref > 0) {
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73 release(&ftable.lock);
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74 return;
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75 }
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76
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77 ff = *f;
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78 f->ref = 0;
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79 f->type = FD_NONE;
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80 release(&ftable.lock);
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81
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82 if (ff.type == FD_PIPE) {
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83 pipeclose(ff.pipe, ff.writable);
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84
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85 } else if (ff.type == FD_INODE) {
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86 begin_trans();
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87 iput(ff.ip);
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88 commit_trans();
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89 }
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90 }
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91
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92 // Get metadata about file f.
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93 int filestat (struct file *f, struct stat *st)
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94 {
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95 if (f->type == FD_INODE) {
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96 ilock(f->ip);
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97 stati(f->ip, st);
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98 iunlock(f->ip);
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99
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100 return 0;
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101 }
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102
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103 return -1;
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104 }
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105
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106 __ncode cbc_fileread1 (int r)
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107 {
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108 struct file *f = proc->cbc_arg.cbc_console_arg.f;
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109 __code (*next)(int ret) = cbc_ret;
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110 if (r > 0)
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111 f->off += r;
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112 iunlock(f->ip);
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113 goto next(r);
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114 }
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115
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116 __ncode cbc_fileread (struct file *f, char *addr, int n, __code (*next)(int ret))
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117 {
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118 if (f->readable == 0) {
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119 goto next(-1);
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120 }
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121
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122 if (f->type == FD_PIPE) {
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123 goto cbc_piperead(f->pipe, addr, n, next);
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124 goto next(-1);
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125 }
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126
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127 if (f->type == FD_INODE) {
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128 ilock(f->ip);
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129 proc->cbc_arg.cbc_console_arg.f = f;
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130 goto cbc_readi(f->ip, addr, f->off, n, cbc_fileread1);
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131 }
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132
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133 goto cbc_panic("fileread");
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134 }
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135
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136 // Read from file f.
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137 int fileread (struct file *f, char *addr, int n)
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138 {
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139 int r;
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140
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141 if (f->readable == 0) {
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142 return -1;
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143 }
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144
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145 if (f->type == FD_PIPE) {
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146 return piperead(f->pipe, addr, n);
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147 }
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148
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149 if (f->type == FD_INODE) {
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150 ilock(f->ip);
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151
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152 if ((r = readi(f->ip, addr, f->off, n)) > 0) {
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153 f->off += r;
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154 }
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155
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156 iunlock(f->ip);
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157
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158 return r;
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159 }
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160
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161 panic("fileread");
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162 }
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163
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164 //PAGEBREAK!
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165 // Write to file f.
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166 int filewrite (struct file *f, char *addr, int n)
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167 {
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168 int r;
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169 int i;
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170 int max;
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171 int n1;
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172
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173 if (f->writable == 0) {
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174 return -1;
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175 }
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176
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177 if (f->type == FD_PIPE) {
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178 return pipewrite(f->pipe, addr, n);
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179 }
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180
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181 if (f->type == FD_INODE) {
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182 // write a few blocks at a time to avoid exceeding
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183 // the maximum log transaction size, including
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184 // i-node, indirect block, allocation blocks,
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185 // and 2 blocks of slop for non-aligned writes.
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186 // this really belongs lower down, since writei()
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187 // might be writing a device like the console.
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188 max = ((LOGSIZE - 1 - 1 - 2) / 2) * 512;
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189 i = 0;
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190
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191 while (i < n) {
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192 n1 = n - i;
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193
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194 if (n1 > max) {
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195 n1 = max;
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196 }
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197
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198 begin_trans();
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199 ilock(f->ip);
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200
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201 if ((r = writei(f->ip, addr + i, f->off, n1)) > 0) {
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202 f->off += r;
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203 }
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204
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205 iunlock(f->ip);
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206 commit_trans();
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207
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208 if (r < 0) {
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209 break;
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210 }
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211
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212 if (r != n1) {
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213 panic("short filewrite");
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214 }
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215
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216 i += r;
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217 }
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218
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219 return i == n ? n : -1;
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220 }
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221
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222 panic("filewrite");
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223 }
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224
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