/*
    * Copyright (C) 2021 Jo-Philipp Wich <jo@mein.io>
    *
    * Permission to use, copy, modify, and/or distribute this software for any
    * purpose with or without fee is hereby granted, provided that the above
    * copyright notice and this permission notice appear in all copies.
    *
    * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <string.h>
  #include <errno.h>
  #include <endian.h>
  
  #include "ucode/source.h"
  
  
  uc_source_t *
  uc_source_new_file(const char *path)
  {
          FILE *fp = fopen(path, "rb");
          uc_source_t *src;
  
          if (!fp)
                  return NULL;
  
          src = xalloc(ALIGN(sizeof(*src)) + strlen(path) + 1);
          src->fp = fp;
          src->buffer = NULL;
          src->filename = strcpy((char *)src + ALIGN(sizeof(*src)), path);
  
          src->usecount = 1;
  
          src->lineinfo.count = 0;
          src->lineinfo.entries = NULL;
  
          return src;
  }
  
  uc_source_t *
  uc_source_new_buffer(const char *name, char *buf, size_t len)
  {
          FILE *fp = fmemopen(buf, len, "rb");
          uc_source_t *src;
  
          if (!fp)
                  return NULL;
  
          src = xalloc(ALIGN(sizeof(*src)) + strlen(name) + 1);
          src->fp = fp;
          src->buffer = buf;
          src->filename = strcpy((char *)src + ALIGN(sizeof(*src)), name);
  
          src->usecount = 1;
  
          src->lineinfo.count = 0;
          src->lineinfo.entries = NULL;
  
          return src;
  }
  
  size_t
  uc_source_get_line(uc_source_t *source, size_t *offset)
  {
          uc_lineinfo_t *lines = &source->lineinfo;
          size_t i, pos = 0, line = 0, lastoff = 0;
  
          for (i = 0; i < lines->count; i++) {
                  if (lines->entries[i] & 0x80) {
                          lastoff = pos;
                          line++;
                          pos++;
                  }
  
                  pos += (lines->entries[i] & 0x7f);
  
                  if (pos >= *offset) {
                          *offset -= lastoff - 1;
  
                          return line;
                  }
          }
  
          return 0;
  }
  
  uc_source_t *
  uc_source_get(uc_source_t *source)
  {
          if (!source)
                  return NULL;
  
          source->usecount++;
 
         return source;
 }
 
 void
 uc_source_put(uc_source_t *source)
 {
         if (!source)
                 return;
 
         if (source->usecount > 1) {
                 source->usecount--;
 
                 return;
         }
 
         uc_vector_clear(&source->lineinfo);
         fclose(source->fp);
         free(source->buffer);
         free(source);
 }
 
 uc_source_type_t
 uc_source_type_test(uc_source_t *source)
 {
         union { char s[sizeof(uint32_t)]; uint32_t n; } buf;
         uc_source_type_t type = UC_SOURCE_TYPE_PLAIN;
         FILE *fp = source->fp;
         size_t rlen;
         int c = 0;
 
         if (fread(buf.s, 1, 2, fp) == 2 && !strncmp(buf.s, "#!", 2)) {
                 source->off += 2;
 
                 while ((c = fgetc(fp)) != EOF) {
                         source->off++;
 
                         if (c == '\n')
                                 break;
                 }
         }
         else {
                 if (fseek(fp, 0L, SEEK_SET) == -1)
                         fprintf(stderr, "Failed to rewind source buffer: %s\n", strerror(errno));
         }
 
         rlen = fread(buf.s, 1, 4, fp);
 
         if (rlen == 4 && buf.n == htobe32(UC_PRECOMPILED_BYTECODE_MAGIC)) {
                 type = UC_SOURCE_TYPE_PRECOMPILED;
         }
         else {
                 uc_source_line_update(source, source->off);
 
                 if (c == '\n')
                         uc_source_line_next(source);
         }
 
         if (fseek(fp, -(long)rlen, SEEK_CUR) == -1)
                 fprintf(stderr, "Failed to rewind source buffer: %s\n", strerror(errno));
 
         return type;
 }
 
 /* lineinfo is encoded in bytes: the most significant bit specifies whether
  * to advance the line count by one or not, while the remaining 7 bits encode
  * the amounts of bytes on the current line.
  *
  * If a line has more than 127 characters, the first byte will be set to
  * 0xff (1 1111111) and subsequent bytes will encode the remaining characters
  * in bits 1..7 while setting bit 8 to 0. A line with 400 characters will thus
  * be encoded as 0xff 0x7f 0x7f 0x13 (1:1111111 + 0:1111111 + 0:1111111 + 0:1111111).
  *
  * The newline character itself is not counted, so an empty line is encoded as
  * 0x80 (1:0000000).
  */
 
 void
 uc_source_line_next(uc_source_t *source)
 {
         uc_lineinfo_t *lines = &source->lineinfo;
 
         uc_vector_grow(lines);
         lines->entries[lines->count++] = 0x80;
 }
 
 void
 uc_source_line_update(uc_source_t *source, size_t off)
 {
         uc_lineinfo_t *lines = &source->lineinfo;
         uint8_t *entry, n;
 
         if (!lines->count)
                 uc_source_line_next(source);
 
         entry = uc_vector_last(lines);
 
         if ((entry[0] & 0x7f) + off <= 0x7f) {
                 entry[0] += off;
         }
         else {
                 off -= (0x7f - (entry[0] & 0x7f));
                 entry[0] |= 0x7f;
 
                 while (off > 0) {
                         n = (off > 0x7f) ? 0x7f : off;
                         uc_vector_grow(lines);
                         entry = uc_vector_last(lines);
                         entry[1] = n;
                         off -= n;
                         lines->count++;
                 }
         }
 }
 

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