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 <errno.h>  //errno
  17 /* Posix */
  18 #include <err.h>    //warnx
  19 #include <stdlib.h> //exit
  20 #include <unistd.h> //chdir
  21 #include <dirent.h> //opendir
  22
  23 #include "parser.tab.h"
  24 /* Public */
  25 int scanner_init(void);
  26 int scanner(void);
  27 /* Private */
  28 #ifndef DL_STACKSIZE
  29 #define DL_STACKSIZE     64
  30 #endif
  31 #ifndef DL_CD_STACKSIZE
  32 #define DL_CD_STACKSIZE  DL_STACKSIZE //square tree
  33 #endif
  34 extern //lexer.c
  35 int  lexer_lex(const char*);
  36 extern //lexer.c
  37 void lexer_pushtok(int, int);
  38 static
  39 int  dredge_current_depth(void);
  40 extern //lexer.c
  41 struct dirent* lexer_direntpa[];
  42 extern //SRC_DIR/bin/tools/apc.c
  43 const char* cargs['Z'];
  44
  45 struct dirlist
  46 { DIR*           dirp;
  47   struct dirent* child_directory_stack[DL_CD_STACKSIZE],** cds;
  48 } directory_list_stack[DL_STACKSIZE + 1],* dls; //+1 for the root dir
  49
  50 /* Directory Listing Stack
  51    FILO Stack for keeping an open DIR* at each directory depth for treewalk.
  52    This stack is depth-safe, checking its depth during push operations, but not
  53    during pop operations, to ensure the thread doesn't open too many files at
  54    once (512 in c runtime), or traverse too far through symbolic links.
  55    A directory listing includes a DIR* and all DIR-typed entity in the directory
  56    as recognized by dirent, populated externally (and optionally).
  57    This stack behaves abnormally by incrementing its PUSH operation prior to
  58    evaluation, and the POP operations after evaluation.  This behavior allows
  59    the 'DL_CURDEPTH' operation to map to the current element in the 'dl_stack'
  60    array, and it is always treated as the "current depth". This also allows us
  61    to init the root directory to 'directory_list_stack'[0] and pop it in a safe
  62    and explicit manner.
  63 */
  64 #define DL_STACK        (directory_list_stack)
  65 #define DL_STACKP       (dls)
  66 #define DL_CD_STACK     ((*DL_STACKP).child_directory_stack)
  67 #define DL_CD_STACKP    ((*DL_STACKP).cds)
  68 #define DL_CURDIR()     ((*DL_STACKP).dirp)
  69 #define DL_LEN()        (DL_STACKP - DL_STACK)
  70 #define DL_CD_LEN()     (DL_CD_STACKP - DL_CD_STACK)
  71 #define DL_INIT()       (DL_STACKP = DL_STACK)
  72 #define DL_CD_INIT()    (DL_CD_STACKP = DL_CD_STACK)
  73 #define DL_POP()        ((*DL_STACKP--).dirp)
  74 #define DL_CD_POP()     (*--DL_CD_STACKP)
  75 #define DL_PUSH(D)      ((*++DL_STACKP).dirp = D)
  76 #define DL_CD_PUSH(E)   (*DL_CD_STACKP++ = E)
  77
  78
  79 /* Initializer
  80    Initializer expects a function pointer to its lexical analysis function.
  81    Sets up stack pointers and returns boolean true if 'opendir' encounters an
  82    error, or if dredge_current_depth returns boolean true.
  83 */
  84 int scanner_init
  85 #define CWDSTR  "./"
  86 #define ROOTDIR (cargs['r'] ? cargs['r'] : CWDSTR)
  87 ()
  88 { DL_INIT();
  89   DL_STACK[0].dirp = opendir(ROOTDIR);
  90   return DL_STACK[0].dirp == NULL || dredge_current_depth() == 0;
  91 }
  92
  93 /* Scanner
  94    The main driver of the scanner will advance the current treewalk state and
  95    tokenize tree-based push/pop operations.  It will call 'lexer_lex' to
  96    tokenize directory names prior to making a push operation. safe checking for
  97    all returns from the filesystem handler will exit on serious system errors.
  98
  99    after pushing a new directory to the directory list, the scanner will dredge
 100    the directory and alphabetically sort all file entries into the lexer's file
 101    array, while placing all subdirectory entries in the current depth's child
 102    directory stack to the scanned later.
 103
 104    Returns the number of elements added to the lexer's file array.
 105 */
 106 int scanner
 107 #define $($)#$ //stringifier
 108 #define ERR_CHILD  "Fatal: Maximum of " $(DL_CD_STACKSIZE)      \
 109   " child directories exceeded for directory at depth %i\n"     \
 110   ,DL_LEN()
 111 #define ERR_DEPTH  "Fatal: Maximum directory depth of " $(DL_STACKSIZE) \
 112   " exceeded during directory scan\n"
 113 #define ERR_DL     "Fatal: Directory List Stack Corruption %x\n", DL_LEN()
 114 #define TOK_CLOPEN  0x55, 0 //TODO
 115 #define TOK_CLCLOSE 0x56, 0 //TODO
 116 ()
 117 { struct dirent* direntp;
 118   struct DIR* DIRp;
 119  parse:
 120   if (DL_CD_LEN() >= DL_CD_STACKSIZE)//fail if maxchildren exceeded
 121     { fprintf(stderr, ERR_CHILD);
 122       goto fail;
 123     }
 124   if (DL_CD_LEN() > 0)             //There are entities to process at this depth
 125     { if ((direntp = DL_CD_POP()) == NULL)  //If the dirent is null, the library
 126         goto libfail;                 //function in dirent has failed
 127       lexer_lex(direntp->d_name);     //lex the directory name
 128       if (DL_LEN() >= DL_STACKSIZE)   //fail if maxdepth exceeded
 129         { fprintf(stderr, ERR_DEPTH);
 130           goto fail;
 131         }
 132       if (chdir(direntp->d_name))     //move into the new directory
 133         goto libfail;
 134       DL_PUSH(opendir(CWDSTR));
 135       if (DL_CURDIR() == NULL)   //open the cwd
 136         { printf("DL_PUSH(opendir failed.\n");
 137           goto libfail;
 138         }
 139       lexer_pushtok(TOK_CLOPEN);      //Push "Open Directory" token
 140       return dredge_current_depth();  //Filter and sort the current depth
 141     }
 142   else if (DL_LEN() >= 0)       //Any dirs left? (Including root)
 143     { if (closedir(DL_POP()))         //close the directory we just left
 144         goto libfail;
 145       lexer_pushtok(TOK_CLCLOSE);     //Push "Close Directory" token
 146       if (DL_LEN() == -1)             //If we just popped root, we're done
 147         return 0;
 148       if (!chdir(".."))               //Move up a directory and start over
 149         goto parse;
 150     }
 151   fprintf(stderr, ERR_DL);
 152  libfail:
 153   perror("parsedir");
 154  fail:
 155   exit(EXIT_FAILURE);
 156 }
 157
 158 /* Directory Entity Sort and Filter (Dredge)
 159    This filter removes all unhandled file types, and places any 'DT_DIR' type
 160    files in the current Directory List's directory stack.  Upon finishing,
 161    the 'CE_STACK' is sorted alphabetically, and the current 'DL_CD_STACK' is
 162    populated.  Prints warnings for unhandled files.
 163
 164    Returns -1 if 'readdir' encounters an error, otherwise returns the number of
 165    directory entries sent to the external 'lexer_direntpa' array.
 166 */
 167 typedef
 168 int (*qcomp)(const void*, const void*);
 169 static inline
 170 int dredge_current_depth
 171 #define READDIR_ERROR (-1)
 172 #define READDIR_DONE  (0)
 173 #define DPS_LEN()     (direntpp - lexer_direntpa)
 174 #define DPS_PUSH(E)   (*direntpp++ = E)
 175 ()
 176 { struct dirent**  direntpp = lexer_direntpa;
 177   DIR*             cwd      = DL_CURDIR();
 178   struct dirent*   direntp;
 179   DL_CD_INIT();
 180  scan_next:
 181   if ((direntp = readdir(cwd)) != NULL)
 182     { switch (direntp->d_type)
 183         { case DT_REG:
 184             DPS_PUSH(direntp);
 185             goto scan_next;
 186           case DT_DIR:
 187             DL_CD_PUSH(direntp);
 188             goto scan_next;
 189           case DT_UNKNOWN:
 190             warnx("unknown file %s: ignoring", direntp->d_name);
 191           default:
 192             goto scan_next;
 193         }
 194     }
 195   if (errno)
 196     return -1;
 197   qsort(lexer_direntpa, DPS_LEN(), sizeof direntp, (qcomp)alphasort);
 198   return DPS_LEN();
 199 }
 200