1 | /*
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2 | =============================================================================
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3 | blkrd.c -- read a block of 0..32767 sectors
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4 | Version 10 -- 1988-01-08 -- D.N. Lynx Crowe
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5 |
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6 | int
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7 | blkrd(fcp, buf, ns)
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8 | struct fcb *fcp;
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9 | char *buf;
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10 | int ns;
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11 |
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12 | Reads 'ns' sectors from file 'fcp' into 'buf'.
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13 | Returns the number of unread sectors, or 0 if all were read.
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14 |
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15 | long
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16 | _secrd(buf, rec)
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17 | register char *buf;
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18 | register short rec;
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19 |
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20 | Reads a logical sector via the track buffer.
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21 | Functionally equivalent to the BIOS B_RDWR read function
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22 | with the addition of transparent write-thru track buffering.
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23 | =============================================================================
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24 | */
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25 |
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26 | #define DEBUGIT 0
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27 |
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28 | #include "stddefs.h"
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29 | #include "biosdefs.h"
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30 | #include "errno.h"
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31 | #include "errdefs.h"
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32 | #include "fspars.h"
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33 |
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34 | #include "memory.h"
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35 |
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36 | /* |
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37 |
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38 | */
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39 |
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40 | #if DEBUGIT
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41 | extern short fsdebug; /* file system debug switch */
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42 | #endif
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43 |
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44 | extern int16_t _nsic(struct fcb *fcp, struct bpb *bpp, int8_t *fp);
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45 |
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46 | extern int32_t _berrno; /* last file system bios error number */
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47 |
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48 | extern uint16_t _thefat[]; /* current file allocation table */
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49 |
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50 | extern struct bpb *_thebpb; /* current bios parameter block */
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51 |
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52 | #if TBUFFER
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53 |
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54 | /* WARNING: this ONLY works for 512 byte sectors, 9 sectors per track */
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55 |
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56 | extern int16_t _b_tbuf[9][256]; /* the track buffer */
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57 |
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58 | extern int16_t _b_trak; /* current track */
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59 | extern int16_t _b_side; /* current side */
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60 | extern int16_t _b_sect; /* current sector */
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61 | extern int16_t _b_tsec; /* current base sector of current track */
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62 |
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63 | #endif
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64 |
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65 | /* |
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66 |
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67 | */
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68 |
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69 | #if TBUFFER
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70 |
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71 | /*
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72 | =============================================================================
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73 | _secrd(buf, rec) -- read a logical sector via the track buffer
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74 | =============================================================================
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75 | */
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76 |
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77 | int32_t _secrd(int8_t *buf, int16_t rec)
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78 | {
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79 | register int16_t track, side, sector;
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80 | int32_t brc;
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81 |
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82 | if (_thebpb->dspt NE 9) /* make sure we can do this */
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83 | return(ERR07);
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84 |
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85 | if (_thebpb->recsiz NE 512)
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86 | return(ERR07);
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87 |
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88 | track = rec / _thebpb->dspc; /* desired track */
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89 | _b_tsec = track * _thebpb->dspc; /* base sector of track */
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90 | sector = rec - _b_tsec; /* logical sector in cylinder */
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91 |
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92 | if (sector GE _thebpb->dspt) { /* adjust sector and side */
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93 |
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94 | sector -= _thebpb->dspt; /* sector now in track */
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95 | side = 1;
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96 | _b_tsec += _thebpb->dspt;
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97 |
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98 | } else {
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99 |
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100 | side = 0;
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101 | }
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102 |
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103 | #if DEBUGIT
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104 | if (fsdebug)
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105 | printf("_secrd($%08.8LX, %d): track=%d, side=%d, sector=%d, _b_tsec=%d\n",
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106 | buf, rec, track, side, sector, _b_tsec);
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107 | #endif
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108 |
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109 | if ((track NE _b_trak) OR (side NE _b_side)) { /* track in buffer ? */
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110 |
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111 | if (brc = BIOS(B_RDWR, 0, &_b_tbuf, _thebpb->dspt, _b_tsec, 0)) {
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112 |
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113 | _b_trak = -1;
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114 | _b_side = -1;
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115 | return(brc);
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116 | }
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117 |
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118 | _b_trak = track;
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119 | _b_side = side;
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120 | }
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121 |
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122 | memcpy(buf, (int8_t *)_b_tbuf[sector], 512);
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123 | return(0L);
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124 | }
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125 |
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126 | #endif
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127 |
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128 | /* |
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129 |
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130 | */
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131 |
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132 | /*
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133 | =============================================================================
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134 | blkrd(fcp, buf, ns) -- read 'ns' sectors from file 'fcp' into 'buf'.
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135 | Returns the number of unread sectors, or 0 if all were read.
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136 | =============================================================================
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137 | */
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138 |
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139 | int16_t blkrd(struct fcb *fcp, int8_t *buf, int16_t ns)
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140 | {
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141 | register int32_t brc; /* bios return code */
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142 | register int16_t rb; /* _nsic return code */
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143 |
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144 | if (ns < 0) /* can't read a negative number of sectors */
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145 | return(ns);
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146 |
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147 | while (ns--) { /* read a sector at a time */
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148 |
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149 | #if DEBUGIT
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150 | if (fsdebug)
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151 | printf("_blkrd(): ns=%d, buf=$%08.8lX, curlsn=%ld, curdsn=%ld, offset=%u\n",
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152 | ns, buf, fcp->curlsn, fcp->curdsn, fcp->offset);
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153 | #endif
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154 |
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155 | #if TBUFFER
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156 | if (brc = _secrd(buf, (int16_t)fcp->curdsn)) {
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157 | #else
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158 | if (brc = BIOS(B_RDWR, 0, buf, 1, (short)fcp->curdsn, 0)) {
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159 | #endif
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160 |
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161 | _berrno = brc; /* log the error */
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162 | errno = EIO;
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163 | return(ns); /* return unread sector count */
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164 | }
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165 |
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166 | if (rb = _nsic(fcp, _thebpb, _thefat)) { /* find next sector */
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167 |
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168 | if (rb EQ -1) /* see if we had an error */
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169 | errno = EIO; /* set error number */
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170 |
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171 | return(ns); /* return unread sector count */
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172 | }
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173 |
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174 | buf += _thebpb->recsiz; /* advance buffer pointer */
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175 | }
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176 |
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177 | return(0); /* return -- all sectors read */
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178 | }
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