Added first cut of reader and writer, but nothing working at this stage.

src/conspage.c

@@ -27,7 +27,13 @@
 bool conspageinitihasbeencalled = false;
 
 /**
- * The (global) pointer to the (global) freelist. Not sure whether this ultimately belongs in this file.
+ * the number of cons pages which have thus far been initialised.
+ */
+int initialisedconspages = 0;
+
+/**
+ * The (global) pointer to the (global) freelist. Not sure whether this ultimately 
+ * belongs in this file.
  */
 struct cons_pointer freelist = NIL;
 
@@ -36,11 +42,6 @@ struct cons_pointer freelist = NIL;
  */
 struct cons_page* conspages[NCONSPAGES];
 
-/**
- * the number of cons pages which have thus far been initialised.
- */
-int initialisedconspages = 0;
-
 
 /**
  * Make a cons page whose serial number (i.e. index in the conspages directory) is pageno.
@@ -55,21 +56,21 @@ void makeconspage() {
       if ( initialisedconspages == 0 && i < 2) {
         if ( i == 0) {
           /* initialise cell as NIL */
-          strncpy( result->cell[i].tag, NILTAG, 4);
-          result->cell[i].count = (2 ^ 32) - 1; // should be max value of unsigned 32 bit integer
+          strncpy( result->cell[i].tag, NILTAG, TAGLENGTH);
+          result->cell[i].count = MAXREFERENCE;
           result->cell[i].payload.free.car = NIL;
           result->cell[i].payload.free.cdr = NIL;
         } else if ( i == 1) {
           /* initialise cell as T */
-          strncpy( result->cell[i].tag, TRUETAG, 4);
-          result->cell[i].count = (2 ^ 32) - 1; // should be max value of unsigned 32 bit integer
+          strncpy( result->cell[i].tag, TRUETAG, TAGLENGTH);
+          result->cell[i].count = MAXREFERENCE;
           result->cell[i].payload.free.car = (struct cons_pointer){ 0, 1};
           result->cell[i].payload.free.cdr = (struct cons_pointer){ 0, 1};
         }
       }
 
       /* otherwise, standard initialisation */
-      strncpy( result->cell[i].tag, FREETAG, 4);
+      strncpy( result->cell[i].tag, FREETAG, TAGLENGTH);
       result->cell[i].payload.free.car = NIL;
       result->cell[i].payload.free.cdr = freelist;
       freelist.page = initialisedconspages;
@@ -85,6 +86,20 @@ void makeconspage() {
 }
 
 
+/**
+ * dump the allocated pages to this output stream.
+ */
+void dumppages( FILE* output) {
+  for ( int i = 0; i < initialisedconspages; i++) {
+    fprintf( output, "\nDUMPING PAGE %d\n", i);
+
+    for ( int j = 0; j < CONSPAGESIZE; j++) {
+      dump_object( output, (struct cons_pointer){i, j});
+    }
+  }
+}
+
+
 /**
  * Frees the cell at the specified pointer. Dangerous, primitive, low
  * level.
@@ -129,10 +144,17 @@ struct cons_pointer allocatecell( char* tag) {
 
     freelist = cell.payload.free.cdr;
 
+    fprintf( stderr, "Before: %c\n", cell.tag[0]);
     strncpy( cell.tag, tag, 4);
+    fprintf( stderr, "After: %c\n", cell.tag[0]);
+    
     cell.count = 1;
     cell.payload.cons.car = NIL;
     cell.payload.cons.cdr = NIL;
+
+    fprintf( stderr, "Allocated cell of type '%s' at %d, %d \n",
+	     tag, result.page, result.offset);
+    dump_object( stderr, result);
   }
 
   return result;

src/conspage.h

@@ -9,14 +9,14 @@
  * the size which, by version 1, it will default to) is the maximum value of an unsigned 32
  * bit integer, which is to say 4294967296. However, we'll start small.
  */
-#define CONSPAGESIZE 256
+#define CONSPAGESIZE 64
 
 /**
  * the number of cons pages we will initially allow for. For convenience we'll set up an array
  * of cons pages this big; however, later we will want a mechanism for this to be able to grow
  * dynamically to the maximum we can currently allow, which is 4294967296.
  */
-#define NCONSPAGES 256
+#define NCONSPAGES 64
 
 /**
  * a cons page is essentially just an array of cons space objects. It might later have a local
@@ -28,9 +28,45 @@ struct cons_page {
 };
 
 
+/**
+ * The (global) pointer to the (global) freelist. Not sure whether this ultimately 
+ * belongs in this file.
+ */
+extern struct cons_pointer freelist;
+
+/**
+ * An array of pointers to cons pages.
+ */
+extern struct cons_page* conspages[NCONSPAGES];
+
+
+/**
+ * Frees the cell at the specified pointer. Dangerous, primitive, low
+ * level.
+ *
+ * @pointer the cell to free
+ */
+void free_cell(struct cons_pointer pointer);
+
+
+/**
+ * Allocates a cell with the specified tag. Dangerous, primitive, low
+ * level.
+ *
+ * @param tag the tag of the cell to allocate - must be a valid cons space tag.
+ * @return the cons pointer which refers to the cell allocated.
+ */
+struct cons_pointer allocatecell( char* tag);
+
+
 /**
  * initialise the cons page system; to be called exactly once during startup.
  */
 void conspagesinit();
 
+/**
+ * dump the allocated pages to this output stream.
+ */
+void dumppages( FILE* output);
+
 #endif

src/consspaceobject.c

@@ -8,7 +8,76 @@
  *  Licensed under GPL version 2.0, or, at your option, any later version.
  */
 
-
 #include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 
+#include "conspage.h"
 #include "consspaceobject.h"
+
+
+/**
+ * increment the reference count of the object at this cons pointer.
+ *
+ * You can't roll over the reference count. Once it hits the maximum
+ * value you cannot increment further.
+ */
+void incref( struct cons_pointer pointer) {
+  struct cons_space_object cell = pointer2cell( pointer);
+
+  if (cell.count < MAXREFERENCE) {
+    cell.count ++;
+  }
+}
+
+
+/**
+ * Decrement the reference count of the object at this cons pointer.
+ *
+ * If a count has reached MAXREFERENCE it cannot be decremented.
+ * If a count is decremented to zero the cell should be freed.
+ */
+void decref( struct cons_pointer pointer) {
+  struct cons_space_object cell = pointer2cell( pointer);
+
+  if (cell.count < MAXREFERENCE) {
+    cell.count --;
+
+    if (cell.count == 0) {
+      free_cell( pointer);
+    }
+  }
+}
+
+
+/**
+ * dump the object at this cons_pointer to this output stream.
+ */
+void dump_object( FILE* output, struct cons_pointer pointer) {
+    struct cons_space_object cell = conspages[pointer.page]->cell[pointer.offset];
+    char * tag = malloc( TAGLENGTH + 1);
+    memset( tag, 0, TAGLENGTH + 1);
+    strncpy( tag, cell.tag, TAGLENGTH);
+
+    fprintf( output, "\tDumping object at page %d, offset %d with tag %s, count %d\n",
+	     pointer.page,
+	     pointer.offset,
+	     tag,
+	     cell.count);
+
+    if ( strncmp( tag, CONSTAG, TAGLENGTH) == 0) {
+      fprintf( output, "\tCons cell: car at page %d offset %d, cdr at page %d offset %d\n",
+	       cell.payload.cons.car.page, cell.payload.cons.car.offset, cell.payload.cons.cdr.page, cell.payload.cons.cdr.offset);
+    } else if ( strncmp( tag, INTEGERTAG, TAGLENGTH) == 0) {
+      fprintf( output, "\t\tInteger cell: value %ld\n", cell.payload.integer.value);
+    } else if ( strncmp( tag, FREETAG, TAGLENGTH) == 0) {
+      fprintf( output, "\t\tFree cell: next at page %d offset %d\n",
+	       cell.payload.cons.cdr.page, cell.payload.cons.cdr.offset);
+    } else if ( strncmp( tag, REALTAG, TAGLENGTH) == 0) {
+      fprintf( output, "\t\tReal cell: value %Lf\n", cell.payload.real.value);
+    } else if ( strncmp( tag, STRINGTAG, TAGLENGTH) == 0) {
+      fprintf( output, "\t\tString cell: character '%c' next at page %d offset %d\n",
+	       cell.payload.string.character, cell.payload.string.cdr.page,
+	       cell.payload.string.cdr.offset);
+    };
+}

src/consspaceobject.h

@@ -8,8 +8,8 @@
  *  Licensed under GPL version 2.0, or, at your option, any later version.
  */
 
-
 #include <stdint.h>
+#include <stdio.h>
 
 #ifndef __consspaceobject_h
 #define __consspaceobject_h
@@ -38,11 +38,33 @@
  */
 #define NIL (struct cons_pointer){ 0, 0}
 
+/**
+ * the maximum possible value of a reference count
+ */
+#define MAXREFERENCE ((2 ^ 32) - 1)
+
 /**
  * a macro to convert a tag into a number
  */
 #define tag2uint(tag) ((uint32_t)*tag)
 
+#define pointer2cell(pointer) ((conspages[pointer.page]->cell[pointer.offset]))
+
+
+/**
+ * true if conspointer points to the special cell NIL, else false 
+ */
+#define nilp(conspoint) (strncmp(pointer2cell(conspoint).tag, NILTAG, TAGLENGTH)==0)
+
+/**
+ * true if conspointer points to a cons cell, else false 
+ */
+#define consp(conspoint) (strncmp(pointer2cell(conspoint).tag, CONSTAG, TAGLENGTH)==0)
+
+/**
+ * true if conspointer points to a string cell, else false 
+ */
+#define stringp(conspoint) (strncmp(pointer2cell(conspoint).tag, STRINGTAG, TAGLENGTH)==0)
 
 /**
  * An indirect pointer to a cons cell
@@ -76,7 +98,7 @@ struct free_payload {
  * optional bignum object.
  */
 struct integer_payload {
-  long int integer;
+  long int value;
 };
 
 
@@ -85,7 +107,7 @@ struct integer_payload {
  * precision, but I'm not sure of the detail.
  */
 struct real_payload {
-  long double real;
+  long double value;
 };
 
 /**
@@ -123,4 +145,21 @@ struct cons_space_object {
 };
 
 
+/**
+ * increment the reference count of the object at this cons pointer
+ */
+void incref( struct cons_pointer pointer);
+
+
+/**
+ * decrement the reference count of the object at this cons pointer
+ */
+void decref( struct cons_pointer pointer);
+
+
+/**
+ * dump the object at this cons_pointer to this output stream.
+ */
+void dump_object( FILE* output, struct cons_pointer pointer);
+
 #endif

src/init.c

@@ -14,11 +14,21 @@
 #include "version.h"
 #include "conspage.h"
 #include "consspaceobject.h"
+#include "print.h"
+#include "read.h"
 
 int main (int argc, char *argv[]) {
   printf( "Post scarcity software environment version %s\n", VERSION);
   conspagesinit();
 
+  printf( "Ready\n>>");
+
+  struct cons_pointer input = read( stdin);
+  incref( input);
+  printf( "\n");
+  print( stdout, input);
+
+  dumppages(stdout);
   // printf( "Tag2uint(\"FREE\") = %d\n", tag2uint("FREE"));
   
   return(0);

src/integer.c

@@ -0,0 +1,24 @@
+/**
+ * integer.c
+ *
+ * functions for integer cells.
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include "conspage.h"
+#include "consspaceobject.h"
+#include "read.h"
+
+/**
+ * Allocate an integer cell representing this value and return a cons pointer to it.
+ */
+struct cons_pointer makeinteger( int value) {
+  struct cons_pointer result = allocatecell( INTEGERTAG);
+  struct cons_space_object cell = conspages[result.page]->cell[result.offset];
+  cell.payload.integer.value = value;
+
+  return result;
+}
+  

src/integer.h

@@ -0,0 +1,19 @@
+/**
+ * integer.h
+ *
+ * functions for integer cells.
+ *
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __integer_h
+#define __integer_h
+
+/**
+ * Allocate an integer cell representing this value and return a cons pointer to it.
+ */
+struct cons_pointer makeinteger( int value);
+
+#endif

src/print.c

@@ -0,0 +1,47 @@
+/**
+ * print.c
+ *
+ * First pass at a printer, for bootstrapping.
+ *
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "conspage.h"
+#include "consspaceobject.h"
+#include "integer.h"
+#include "print.h"
+
+void print( FILE* output, struct cons_pointer pointer) {
+  struct cons_space_object cell = pointer2cell( pointer);
+
+  if ( strncmp( cell.tag, CONSTAG, TAGLENGTH) == 0) {
+    fputc( '(', output);
+    for (struct cons_pointer p = pointer; consp( p);
+	 p = pointer2cell( p).payload.cons.cdr) {
+      print( output, p);
+      fputc( ' ', output);
+    }
+    fputc( ')', output);
+  } else if ( strncmp( cell.tag, INTEGERTAG, TAGLENGTH) == 0) {
+    fprintf( output, " %ld", cell.payload.integer.value);
+  } else if ( strncmp( cell.tag, NILTAG, TAGLENGTH) == 0) {
+    fprintf( output, "NIL");
+  } else if ( strncmp( cell.tag, REALTAG, TAGLENGTH) == 0) {
+    fprintf( output, "%Lf", cell.payload.real.value);
+  } else if ( strncmp( cell.tag, STRINGTAG, TAGLENGTH) == 0) {
+    fputc( '"', output);
+    for (struct cons_pointer p = pointer; stringp( p);
+	 p = pointer2cell( p).payload.string.cdr) {
+      fprintf( output, '%c', (char)pointer2cell( p).payload.string.character);
+    }
+    fputc( '"', output);
+  } else if ( strncmp( cell.tag, TRUETAG, TAGLENGTH) == 0) {
+    fprintf( output, "T");
+  }
+}

src/print.h

@@ -0,0 +1,19 @@
+/**
+ * print.h
+ *
+ * First pass at a printer, for bootstrapping.
+ *
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+
+#ifndef __print_h
+#define __print_h
+
+void print( FILE* output, struct cons_pointer pointer);
+
+#endif

src/quickbool.h

@@ -1,19 +0,0 @@
-/**
- * quickbool.h
- *
- * Currently, just a macro to test whether a cons_pointer is the
- * special NIL cons_pointer.
- *
- * (c) 2017 Simon Brooke <simon@journeyman.cc>
- * Licensed under GPL version 2.0, or, at your option, any later version.
- */
-
-#include "consspaceobject.h"
-
-#ifndef __quickbool_h
-#define __quickbool_h
-
-/* true if conspointer points to the special cell NIL, else false */
-#define nilp(conspoint) ((((struct cons_pointer)conspoint).page == NIL.page) && ((struct conspoint).offser == NIL.offset))
-
-#endif

src/read.c

@@ -0,0 +1,92 @@
+/**
+ * read.c
+ *
+ * First pass at a reader, for bootstrapping.
+ *
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+
+#include "consspaceobject.h"
+#include "integer.h"
+#include "read.h"
+
+/* for the time being things which may be read are:
+   strings
+   numbers - either integer or real, but not yet including ratios or bignums
+   lists
+   Can't read atoms because I don't yet know what an atom is or how it's stored. */
+
+/**
+ * read a number from this input stream, given this initial character.
+ */
+struct cons_pointer readnumber( FILE* input, char initial) {
+  int accumulator = 0;
+  char c;
+  
+  for (c = initial; isdigit( c); c = fgetc( input)) {
+    int digitvalue = (int)c - (int)'0';
+    accumulator = accumulator * 10 + digitvalue;
+  }
+
+  /* push back the character read which was not a digit */
+  fputc( c, input);
+
+  return makeinteger( accumulator);
+}
+
+
+struct cons_pointer readlist( FILE* input) {
+  return NIL;
+}
+
+
+struct cons_pointer readstring( FILE* input) {
+  return NIL;
+}
+
+
+/**
+ * read the next object on this input stream and return a cons_pointer to it.
+ */
+struct cons_pointer read( FILE* input) {
+  struct cons_pointer result = NIL;
+
+  char c = fgetc( input);
+
+  while ( isblank( c)) {
+    c = fgetc( input);
+  }
+  
+  switch( c) {
+  case '(' : result = readlist(input);
+    break;
+  case '"': result = readstring(input);
+    break;
+  case '0':
+  case '1':
+  case '2':
+  case '3':
+  case '4':
+  case '5':
+  case '6':
+  case '7':
+  case '8':
+  case '9':
+    // case '.':
+    result = readnumber( input, c);
+    break;
+  default:
+    fprintf( stderr, "Unrecognised start of input character %c\n", c);
+  }
+
+  return result;
+}
+    
+
+
+    

src/read.h

@@ -0,0 +1,19 @@
+/**
+ * read.c
+ *
+ * First pass at a reader, for bootstrapping.
+ *
+ *
+ * (c) 2017 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __read_h
+#define __read_h
+
+/**
+ * read the next object on this input stream and return a cons_pointer to it.
+ */
+struct cons_pointer read( FILE* input);
+
+#endif