Partial decoder (WIP)

1 files changed, 489 insertions, 0 deletions

diff --git a/src/ecbor_decoder.c b/src/ecbor_decoder.c
new file mode 100644
index 0000000..ccc8196
--- /dev/null
+++ b/src/ecbor_decoder.c
@@ -0,0 +1,489 @@
+/*
+ * Copyright (c) 2018 Vasile Vilvoiu <vasi.vilvoiu@gmail.com>
+ *
+ * libecbor is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include "ecbor.h"
+#include "ecbor_internal.h"
+
+static ecbor_error_t
+ecbor_initialize_decode_internal (ecbor_decode_context_t *context,
+                                  const uint8_t *buffer,
+                                  uint64_t buffer_size)
+{
+  if (!context) {
+    return ECBOR_ERR_NULL_CONTEXT;
+  }
+  if (!buffer) {
+    return ECBOR_ERR_NULL_INPUT_BUFFER;
+  }
+
+  context->in_position = buffer;
+  context->bytes_left = buffer_size;
+  
+  return ECBOR_OK;
+}
+
+ecbor_error_t
+ecbor_initialize_decode (ecbor_decode_context_t *context,
+                         const uint8_t *buffer,
+                         uint64_t buffer_size)
+{
+  ecbor_error_t rc =
+    ecbor_initialize_decode_internal (context, buffer, buffer_size);
+
+  if (rc != ECBOR_OK) {
+    return rc;
+  }
+
+  context->mode = ECBOR_MODE_DECODE;
+  context->nodes = NULL;
+  context->node_capacity = 0;
+  context->n_nodes = 0;
+  
+  return ECBOR_OK;
+}
+
+ecbor_error_t
+ecbor_initialize_decode_streamed (ecbor_decode_context_t *context,
+                                  const uint8_t *buffer,
+                                  uint64_t buffer_size)
+{
+  ecbor_error_t rc =
+    ecbor_initialize_decode_internal (context, buffer, buffer_size);
+
+  if (rc != ECBOR_OK) {
+    return rc;
+  }
+  
+  context->mode = ECBOR_MODE_DECODE_STREAMED;
+  context->nodes = NULL;
+  context->node_capacity = 0;
+  context->n_nodes = 0;
+  
+  return ECBOR_OK;
+}
+
+ecbor_error_t
+ecbor_initialize_decode_tree (ecbor_decode_context_t *context,
+                              const uint8_t *buffer,
+                              uint64_t buffer_size,
+                              ecbor_node_t *node_buffer,
+                              uint64_t node_capacity)
+{
+  ecbor_error_t rc =
+    ecbor_initialize_decode_internal (context, buffer, buffer_size);
+
+  if (rc != ECBOR_OK) {
+    return rc;
+  }
+  
+  if (!node_buffer) {
+    return ECBOR_ERR_NULL_ITEM_BUFFER;
+  }
+  
+  context->mode = ECBOR_MODE_DECODE_TREE;
+  context->nodes = node_buffer;
+  context->node_capacity = node_capacity;
+  context->n_nodes = 0;
+  
+  return ECBOR_OK;
+}
+
+static inline ecbor_error_t
+ecbor_decode_uint (ecbor_decode_context_t *context,
+                   uint64_t *value,
+                   uint64_t *size,
+                   uint8_t additional)
+{
+  if (additional < 24) {
+    /* value stored in additional information */
+    (*value) = additional;
+    (*size) = 1;
+  } else {
+    /* compute storage size */
+    (*size) = (0x1 << (additional - ECBOR_ADDITIONAL_1BYTE));
+    if (context->bytes_left < (*size)) {
+      return ECBOR_ERR_INVALID_END_OF_BUFFER;
+    }
+
+    /* read actual value */
+    switch (additional) {
+      case ECBOR_ADDITIONAL_1BYTE:
+        (*value) = *((uint8_t *) context->in_position);
+        break;
+
+      case ECBOR_ADDITIONAL_2BYTE:
+        (*value) = *((uint16_t *) context->in_position);
+        break;
+
+      case ECBOR_ADDITIONAL_4BYTE:
+        (*value) = *((uint32_t *) context->in_position);
+        break;
+
+      case ECBOR_ADDITIONAL_8BYTE:
+        (*value) = *((uint64_t *) context->in_position);
+        break;
+
+      default:
+        return ECBOR_ERR_INVALID_ADDITIONAL;
+    }
+    
+    /* advance buffer */
+    context->in_position += (*size);
+    context->bytes_left -= (*size);
+  }
+  
+  return ECBOR_OK;
+}
+
+static ecbor_error_t
+ecbor_decode_next_internal (ecbor_decode_context_t *context,
+                            ecbor_item_t *item,
+                            int8_t is_chunk,
+                            ecbor_major_type_t chunk_mtype)
+{
+  unsigned int additional;
+
+  if (context->bytes_left == 0) {
+    return ECBOR_END_OF_BUFFER;
+  }
+  if (context->mode != ECBOR_MODE_DECODE
+      && context->mode != ECBOR_MODE_DECODE_STREAMED) {
+    /* only allow known modes of operation; junk in <mode> will generate
+       undefined behaviour */
+    return ECBOR_ERR_WRONG_MODE;
+  }
+  
+  /* clear item, just so we do not leave garbage on partial read */
+  item->major_type = ECBOR_MT_UNDEFINED;
+  item->size = 0;
+  item->n_chunks = 0;
+  item->is_indefinite = false;
+  
+  /* extract major type (most significant three bits) and additional info */
+  item->major_type = (*context->in_position >> 5) & 0x07;
+  additional = (*context->in_position & 0x1f);
+  context->in_position ++; context->bytes_left --;
+  
+  /* check mandatory major type (in case we are reading string chunks);
+     we do not want to continue parsing a malformed indefinite string and
+     potentially explode the stack with subsequent calls */
+  if (is_chunk && chunk_mtype != item->major_type) {
+    if (item->major_type == ECBOR_MT_SPECIAL
+        && additional == ECBOR_ADDITIONAL_INDEFINITE) {
+      /* this is a valid stop code, pass it directly; note that this branch is
+         only taken when inside an indefinite string */
+      return ECBOR_END_OF_INDEFINITE;
+    } else {
+      /* this is not a stop code, and the item has the wrong major type */
+      return ECBOR_ERR_INVALID_CHUNK_MAJOR_TYPE;
+    }
+  }
+  
+  /* handle type */
+  switch (item->major_type) {
+
+    /*
+     * Integer types
+     */
+    case ECBOR_MT_UINT:
+      return ecbor_decode_uint (context, &item->value.uinteger, &item->size,
+                                additional);
+    
+    case ECBOR_MT_NINT:
+      {
+        /* read negative value as unsigned */
+        ecbor_error_t rc = ecbor_decode_uint (context, &item->value.uinteger,
+                                              &item->size, additional);
+        if (rc != ECBOR_OK) {
+          return rc;
+        }
+
+        /* parse as negative */
+        item->value.integer = (-1) - item->value.uinteger;
+      }
+      break;
+
+    /*
+     * String types
+     */
+    case ECBOR_MT_BSTR:
+    case ECBOR_MT_STR:
+      /* keep buffer pointer from current pointer */
+      item->value.string = context->in_position;
+
+      /* discriminate between definite and indefinite strings; we do not treat
+       * indefinite strings as we do indefinite maps and arrays, in the sense
+       * that we do not allow the user to manually walk each chunk
+       */
+      if (additional == ECBOR_ADDITIONAL_INDEFINITE) {
+        ecbor_item_t chunk;
+        ecbor_error_t rc;
+        
+        /* mark accordingly */
+        item->is_indefinite = true;
+        
+        /* do not allow nested indefinite length strings */
+        if (is_chunk) {
+          return ECBOR_ERR_NESTET_INDEFINITE_STRING;
+        }
+
+        /* indefinite lenght string; read through all blocks to compute size */
+        item->value.string = context->in_position;
+        
+        while (true) {
+          /* read next chunk */
+          rc = ecbor_decode_next_internal (context, &chunk, true,
+                                           item->major_type);
+          if (rc != ECBOR_OK) {
+            if (rc == ECBOR_END_OF_INDEFINITE) {
+              /* stop code found, break from loop */
+              break;
+            } else if (rc == ECBOR_END_OF_BUFFER) {
+              /* treat a valid end of buffer as invalid since we did not yet
+                 find the stop code */
+              return ECBOR_ERR_INVALID_END_OF_BUFFER;
+            } else if (rc != ECBOR_OK) {
+              /* other error */
+              return rc;
+            }
+          }
+
+          /* add chunk size to item size */
+          item->size += chunk.size;
+          item->n_chunks ++;
+        }
+      } else {
+        uint64_t foo;
+
+        /* read size of buffer */
+        ecbor_error_t rc = ecbor_decode_uint (context, &item->size, &foo,
+                                              additional);
+        if (rc != ECBOR_OK) {
+          return rc;
+        }
+
+        /* advance */
+        if (context->bytes_left < item->size) {
+          return ECBOR_ERR_INVALID_END_OF_BUFFER;
+        }
+        context->in_position += item->size;
+        context->bytes_left -= item->size;
+      }
+      break;
+
+    /*
+     * Arrays and maps
+     */
+    case ECBOR_MT_ARRAY:
+    case ECBOR_MT_MAP:
+      /* keep buffer pointer from current pointer */
+      item->value.items = context->in_position;
+
+      /* discriminate between definite and indefinite maps and arrays */
+      if (additional == ECBOR_ADDITIONAL_INDEFINITE) {
+        /* mark accordingly */
+        item->is_indefinite = true;
+
+        if (context->mode != ECBOR_MODE_DECODE_STREAMED) {
+          /* we have an indefinite map or array and we're not in streamed mode;
+             we have to walk children to compute size and advance to next item */
+          ecbor_item_t child;
+          ecbor_error_t rc;
+
+          while (true) {
+            /* read next chunk */
+            rc = ecbor_decode_next_internal (context, &child, false,
+                                             ECBOR_MT_UNDEFINED);
+            if (rc != ECBOR_OK) {
+              if (rc == ECBOR_END_OF_INDEFINITE) {
+                /* stop code found, break from loop */
+                break;
+              } else if (rc == ECBOR_END_OF_BUFFER) {
+                /* treat a valid end of buffer as invalid since we did not yet
+                   find the stop code */
+                return ECBOR_ERR_INVALID_END_OF_BUFFER;
+              } else if (rc != ECBOR_OK) {
+                /* other error */
+                return rc;
+              }
+            }
+
+            /* add chunk size to item size */
+            item->size += child.size;
+            item->n_chunks ++;
+          }
+          
+          if ((item->major_type == ECBOR_MT_MAP) && (item->n_chunks % 2 != 0)) {
+            /* incomplete key-value pair; we expect maps to have even number of
+               items */
+            return ECBOR_ERR_INVALID_KEY_VALUE_PAIR;
+          }
+        }
+      } else {
+        uint64_t foo;
+
+        /* read size of map or array */
+        ecbor_error_t rc = ecbor_decode_uint (context, &item->n_chunks, &foo,
+                                              additional);
+        if (rc != ECBOR_OK) {
+          return rc;
+        }
+
+        if (item->major_type == ECBOR_MT_MAP) {
+          /* we keep the total number of items in n_chunks, yet the map has the
+             number of key-value pairs encoded in the length */
+          item->n_chunks *= 2;
+        }
+
+        if (context->mode != ECBOR_MODE_DECODE_STREAMED) {
+          ecbor_item_t child;
+          ecbor_error_t rc;
+          uint64_t child_no;
+
+          /* not in streamed mode; compute size so we can advance */
+          for (child_no = 0; child_no < item->n_chunks; child_no ++) {
+            /* read next child */
+            rc = ecbor_decode_next_internal (context, &child, false,
+                                             ECBOR_MT_UNDEFINED);
+            if (rc != ECBOR_OK) {
+              if (rc == ECBOR_END_OF_INDEFINITE) {
+                /* stop code found, but none is expected */
+                return ECBOR_ERR_INVALID_STOP_CODE;
+              } else if (rc == ECBOR_END_OF_BUFFER) {
+                /* treat a valid end of buffer as invalid since we did not yet
+                   reach the end of the map or array */
+                return ECBOR_ERR_INVALID_END_OF_BUFFER;
+              } else if (rc != ECBOR_OK) {
+                /* other error */
+                return rc;
+              }
+            }
+
+            /* add child size to item size */
+            item->size += child.size;
+          }
+        }
+      }
+      break;
+
+    case ECBOR_MT_TAG:
+      return ECBOR_ERR_CURRENTLY_NOT_SUPPORTED;
+      break;
+
+    case ECBOR_MT_SPECIAL:
+      if (additional == ECBOR_ADDITIONAL_INDEFINITE) {
+        /* stop code */
+        return ECBOR_END_OF_INDEFINITE;
+      } else {
+        return ECBOR_ERR_CURRENTLY_NOT_SUPPORTED;
+      }
+      break;
+    
+    default:
+      return ECBOR_ERR_UNKNOWN;
+  }
+  
+  return ECBOR_OK;
+}
+
+ecbor_error_t
+ecbor_decode (ecbor_decode_context_t *context, ecbor_item_t *item)
+{
+  ecbor_error_t rc = ECBOR_OK;
+  ecbor_node_t *curr_prev = NULL, *curr_parent = NULL, *curr_node = NULL;
+  
+  if (!context) {
+    return ECBOR_ERR_NULL_CONTEXT;
+  }
+  if (!item) {
+    return ECBOR_ERR_NULL_ITEM;
+  }
+
+  if (context->mode == ECBOR_MODE_DECODE
+      || context->mode == ECBOR_MODE_DECODE_STREAMED) {
+    /* we just get the next item */
+    return ecbor_decode_next_internal (context, item, false, ECBOR_MT_UNDEFINED);
+  }
+  
+  /*
+   * decode whole tree
+   */
+  context->n_nodes = 0;
+  
+  /* step into streamed mode; some of the semantic checks will be done here */
+  context->mode = ECBOR_MODE_DECODE_STREAMED;
+
+  /* consume until something happens */
+  while (true) {
+
+    /* allocate new node */
+    if (context->n_nodes >= context->node_capacity) {
+      rc = ECBOR_ERR_END_OF_NODE_BUFFER;
+      goto end;
+    }
+
+    curr_prev = curr_node;
+    curr_node = &context->nodes[context->n_nodes];
+    context->n_nodes ++;
+    
+    if (curr_prev) {
+      curr_prev->next = curr_node;
+      curr_node->index = curr_prev->index + 1;
+    } else {
+      curr_node->index = 0;
+    }
+
+    /* consume next item */
+    rc = ecbor_decode_next_internal (context, &curr_node->item, false,
+                                     ECBOR_MT_UNDEFINED);
+
+    /* handle end of indefinite */
+    if (rc == ECBOR_END_OF_INDEFINITE) {
+      if ((!curr_parent)
+          || (curr_parent->item.major_type != ECBOR_MT_MAP
+              && curr_parent->item.major_type != ECBOR_MT_ARRAY)
+          || (!curr_parent->item.is_indefinite)) {
+        /* we are not in an indefinite map or array */
+        rc = ECBOR_ERR_INVALID_STOP_CODE;
+        goto end;
+      }
+
+      /* jump up one level */
+      curr_node = curr_parent;
+      curr_parent = curr_parent->parent;
+      
+      /* ignore this item, reuse it later */
+      context->n_nodes --;
+      continue;
+    }
+    
+    /* handle new children */
+    if (curr_node->item.major_type == ECBOR_MT_MAP
+        || curr_node->item.major_type == ECBOR_MT_ARRAY) {
+      /* TODO */
+    }
+    
+    /* handle end of definite maps and arrays */
+    /* TODO */
+    
+    /* check return code */
+    if (rc == ECBOR_END_OF_BUFFER) {
+      if (!curr_parent) {
+        /* we are not allowed to reach the end unless the item is top-level */
+        rc = ECBOR_ERR_INVALID_END_OF_BUFFER;
+        goto end;
+      }
+    } else if (rc != ECBOR_OK) {
+      goto end;
+    }
+  }
+
+end:
+  /* return to tree mode and return error code */
+  context->mode = ECBOR_MODE_DECODE_TREE;
+  return rc;
+}
\ No newline at end of file