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