src/apc/scanner.c

   1 /*!@file
   2   \brief   APC Directory Scanner
   3   \details This hand-written parser/scanner traverses a directory tree and
   4            tokenizes elements of the structure which correspond to APC grammar.
   5            The parser is implemented as a 2D stack which populates a list of
   6            child directories at each depth, handling only the leaf nodes
   7            (regular files) of the directory open at the current depth to
   8            conserve memory and speed up traversal.
   9            The scanner works with the lexer to lexically analyze text, and
  10            assumes the existence of an external 'lex' function
  11   \author  Jordan Lavatai
  12   \date    Aug 2016
  13   ----------------------------------------------------------------------------*/
  14 /* Standard */
  15 #include <stdio.h>  //print
  16 #include <string.h> //strncmp
  17 #include <errno.h>  //errno
  18 #include <ctype.h>  //tolower
  19 /* Posix */
  20 #include <err.h>    //warnx
  21 #include <stdlib.h> //exit
  22 #include <unistd.h> //chdir
  23 #include <dirent.h> //opendir
  24 #include <unistr.h> //unicode strings
  25 /* Internal */
  26 #include "parser.tab.h"
  27 /* Public */
  28 int   scanner_init(void);
  29 void  scanner_quit(void);
  30 int   scanner(void);
  31 int   scanner_scanpixels(int*,int);
  32 /* Private */
  33 extern //lexer.c
  34 int   lexer_lexstring(const char*);
  35 extern //lexer.c
  36 void  lexer_pushtok(int, int);
  37 static
  38 int   dredge_current_depth(void);
  39 /* Mem */
  40 extern //lexer.c
  41 struct dirent* lexer_direntpa[], **lexer_direntpp;
  42 extern //SRC_DIR/bin/tools/apc.c
  43 const char* cargs['Z'];
  44 #ifndef DL_STACKSIZE
  45 #define DL_STACKSIZE     64
  46 #endif
  47 #ifndef DL_CD_STACKSIZE
  48 #define DL_CD_STACKSIZE  DL_STACKSIZE //square tree
  49 #endif
  50 static
  51 struct dirlist
  52 { DIR*           dirp;
  53   struct dirent* child_directory_stack[DL_CD_STACKSIZE],** cds;
  54 } directory_list_stack[DL_STACKSIZE + 1],* dls; //+1 for the root dir
  55 static
  56 FILE* current_open_file = NULL;
  57
  58 /* Directory Listing Stack
  59    FILO Stack for keeping an open DIR* at each directory depth for treewalk.
  60    This stack is depth-safe, checking its depth during push operations, but not
  61    during pop operations, to ensure the thread doesn't open too many files at
  62    once (512 in c runtime), or traverse too far through symbolic links.
  63    A directory listing includes a DIR* and all DIR-typed entity in the directory
  64    as recognized by dirent, populated externally (and optionally).
  65    This stack behaves abnormally by incrementing its PUSH operation prior to
  66    evaluation, and the POP operations after evaluation.  This behavior allows
  67    the 'DL_CURDEPTH' operation to map to the current element in the 'dl_stack'
  68    array, and it is always treated as the "current depth". This also allows us
  69    to init the root directory to 'directory_list_stack'[0] and pop it in a safe
  70    and explicit manner.
  71 */
  72 #define DL_STACK        (directory_list_stack)
  73 #define DL_STACKP       (dls)
  74 #define DL_CD_STACK     ((*DL_STACKP).child_directory_stack)
  75 #define DL_CD_STACKP    ((*DL_STACKP).cds)
  76 #define DL_CURDIR()     ((*DL_STACKP).dirp)
  77 #define DL_LEN()        (DL_STACKP - DL_STACK)
  78 #define DL_CD_LEN()     (DL_CD_STACKP - DL_CD_STACK)
  79 #define DL_INIT()       (DL_STACKP = DL_STACK)
  80 #define DL_CD_INIT()    (DL_CD_STACKP = DL_CD_STACK)
  81 #define DL_POP()        ((*DL_STACKP--).dirp)
  82 #define DL_CD()         (*DL_CD_STACKP)
  83 #define DL_CD_CURNAME() (DL_CD()->d_name)
  84 #define DL_CD_POP()     (*--DL_CD_STACKP)
  85 #define DL_PUSH(D)      ((*++DL_STACKP).dirp = D)
  86 #define DL_CD_PUSH(E)   (*DL_CD_STACKP++ = E)
  87
  88
  89 /* Initializer
  90    Initializer expects a function pointer to its lexical analysis function.
  91    Sets up stack pointers and returns boolean true if 'opendir' encounters an
  92    error, or if dredge_current_depth returns boolean true.
  93 */
  94 int scanner_init
  95 #define CWDSTR  "./"
  96 #define ROOTDIR (cargs['d'] ? cargs['d'] : CWDSTR)
  97 ()
  98 { DL_INIT();
  99   DL_STACK[0].dirp = opendir(ROOTDIR);
 100   if (current_open_file != NULL)
 101     { fclose(current_open_file);
 102       current_open_file = NULL;
 103     }
 104   printf("Root dir %s\n",ROOTDIR);
 105   return !chdir(ROOTDIR) && (DL_STACK[0].dirp == NULL || dredge_current_depth() == -1);
 106 }
 107
 108 /* Quit */
 109 void scanner_quit
 110 ()
 111 { if (DL_CURDIR())
 112     closedir(DL_CURDIR());
 113 }
 114
 115 /* Scanner
 116    The main driver of the scanner will advance the current treewalk state and
 117    tokenize tree-based push/pop operations.  It will call 'lexer_lex' to
 118    tokenize directory names prior to making a push operation. safe checking for
 119    all returns from the filesystem handler will exit on serious system errors.
 120
 121    after pushing a new directory to the directory list, the scanner will dredge
 122    the directory and alphabetically sort all file entries into the lexer's file
 123    array, while placing all subdirectory entries in the current depth's child
 124    directory stack to be scanned later.
 125
 126    Returns the number of tokens generated on success, -1 on error.
 127 */
 128 int scanner
 129 #define $($)#$ //stringifier
 130 #define ERR_CHILD  "Fatal: Maximum of " $(DL_CD_STACKSIZE)                  \
 131   " child directories exceeded for directory at depth %i\n"                 \
 132   ,DL_LEN()
 133 #define ERR_DEPTH  "Fatal: Maximum directory depth of " $(DL_STACKSIZE)     \
 134   " exceeded during directory scan\n"
 135 #define ERR_DL     "Fatal: Directory List Stack Corruption %x\n", DL_LEN()
 136 ()
 137 { int ntok = 0;
 138  scan:
 139   if (DL_CD_LEN() >= DL_CD_STACKSIZE)//fail if maxchildren exceeded
 140     { fprintf(stderr, ERR_CHILD);
 141       goto fail;
 142     }
 143   if (DL_CD_LEN() > 0)               //There are entities to process
 144     { if (DL_CD_POP() == NULL)            //If the dirent is null, then the
 145         goto libfail;                       //lib function in dirent has failed
 146       ntok += lexer_lexstring(DL_CD_CURNAME());//lex the directory name
 147       if (DL_LEN() >= DL_STACKSIZE)       //fail if maxdepth exceeded
 148         { fprintf(stderr, ERR_DEPTH);
 149           goto fail;
 150         }
 151       if (chdir(DL_CD_CURNAME()))         //move into the new directory
 152         goto libfail;
 153       DL_PUSH(opendir(CWDSTR));
 154       if (DL_CURDIR() == NULL)            //open the cwd
 155         goto libfail;
 156       lexer_pushtok(CLOPEN, 0);           //Push "Open Directory" token
 157       ntok++;
 158       return dredge_current_depth();      //Filter and sort the current depth
 159     }
 160   else if (DL_LEN() >= 0)            //Any dirs left? (Including root)
 161     { if (closedir(DL_POP()))             //close the directory we just left
 162         goto libfail;
 163       if (DL_LEN() == -1)                 //If we just popped root,
 164         goto done;                          //we're done
 165       lexer_pushtok(CLCLOSE, 0);          //Else push "Close Directory" token,
 166       ntok++;
 167       if (!chdir(".."))                   //move up a directory and
 168         goto scan;                          //start over
 169     }
 170   fprintf(stderr, ERR_DL);
 171  libfail:
 172   perror("scanner: ");
 173  fail:
 174   return -1;
 175  done:
 176   return ntok;
 177 }
 178
 179 /* Scan Pixels
 180    Scans up to 'len' pixels from the current file into 'buf'.
 181    Returns the number of pixels scanned from the file, or -1 on error
 182 */
 183 int scanner_scanpixels
 184 ( int*  buf,
 185   int   max_len
 186 )
 187 { static int col_len, row_len, row;
 188   //Open the current file if not yet open
 189   if (current_open_file == NULL)
 190     { if ((current_open_file = fopen(DL_CD_CURNAME(),"rb")) == NULL)
 191         { perror("fopen: ");
 192           return -1;
 193         }
 194       //Verify file header, get row_len/col_len
 195       if (read_img_header(&row_len, &col_len))
 196         return -1;
 197       row = 0;
 198     }
 199   //Read pixels into the buffer if there are rows left in the image
 200   if (row++ < row_len)
 201     //TODO: return read_img_pixels(buf, col_len);
 202     printf("SCANPIXELS NOT IMPLEMENTED\n.");
 203   //Close the file and return 0
 204   fclose(current_open_file);
 205   current_open_file = NULL;
 206   return 0;
 207 }
 208
 209 /* Directory Entity Sort and Filter (Dredge)
 210    This filter removes all unhandled file types, and places any 'DT_DIR' type
 211    files in the current Directory List's directory stack.  Upon finishing,
 212    the 'CE_STACK' is sorted alphabetically, and the current 'DL_CD_STACK' is
 213    populated.  Prints warnings for unhandled files.
 214
 215    Returns -1 if 'readdir' encounters an error, otherwise returns the number of
 216    directory entries sent to the external 'lexer_direntpa' array.
 217 */
 218 typedef //so we can typecast dirent's 'alphasort()' to take const void*s
 219 int (*qcomp)(const void*, const void*);
 220 static inline
 221 int dredge_current_depth
 222 #define READDIR_ERROR (-1)
 223 #define READDIR_DONE  (0)
 224 #define DPS_LEN()     (lexer_direntpp - lexer_direntpa)
 225 #define DPS_PUSH(E)   (*lexer_direntpp++ = E)
 226 ()
 227 { struct dirent**  direntpp = lexer_direntpa;
 228   DIR*             cwd      = DL_CURDIR();
 229   struct dirent*   direntp;
 230   DL_CD_INIT();
 231  scan_next:
 232   if ((direntp = readdir(cwd)) != NULL)
 233     { switch (direntp->d_type)
 234         { case DT_REG:
 235             DPS_PUSH(direntp);
 236             goto scan_next;
 237           case DT_DIR:
 238             if (*(direntp->d_name) == '.') //skip hidden files and relative dirs
 239               goto scan_next;
 240             DL_CD_PUSH(direntp);
 241             goto scan_next;
 242           case DT_UNKNOWN:
 243             warnx("unknown file %s: ignoring", direntp->d_name);
 244           default:
 245             goto scan_next;
 246         }
 247     }
 248   if (errno)
 249     return -1;
 250   qsort(lexer_direntpa, DPS_LEN(), sizeof direntp, (qcomp)alphasort);
 251   return DPS_LEN();
 252 }