All files / json-pack/src/xdr XdrSchemaDecoder.ts

89.55% Statements 60/67
85.29% Branches 29/34
92.85% Functions 13/14
90.62% Lines 58/64

Press n or j to go to the next uncovered block, b, p or k for the previous block.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 2141x 1x 1x                                       1x     31x 31x             32x 32x             69x     1x   20x   1x   3x   1x   1x   1x   1x       4x       1x   3x   10x       4x   4x   7x   6x               1x               4x     4x 8x 3x         1x             1x             3x     3x 1x     2x             10x     10x 1x     9x             9x             9x     4x 1x     3x             7x   7x 14x     7x               6x     6x 10x 4x 4x         2x 1x 1x     1x                            
import {Reader} from '@jsonjoy.com/buffers/lib/Reader';
import {XdrDecoder} from './XdrDecoder';
import {XdrUnion} from './XdrUnion';
import type {IReader, IReaderResettable} from '@jsonjoy.com/buffers/lib';
import type {
  XdrSchema,
  XdrEnumSchema,
  XdrOpaqueSchema,
  XdrVarlenOpaqueSchema,
  XdrStringSchema,
  XdrArraySchema,
  XdrVarlenArraySchema,
  XdrStructSchema,
  XdrUnionSchema,
  XdrOptionalSchema,
} from './types';
 
/**
 * XDR (External Data Representation) schema-aware decoder.
 * Decodes values according to provided XDR schemas with proper validation.
 * Based on RFC 4506 specification.
 */
export class XdrSchemaDecoder {
  private decoder: XdrDecoder;
 
  constructor(public readonly reader: IReader & IReaderResettable = new Reader()) {
    this.decoder = new XdrDecoder(reader);
  }
 
  /**
   * Decodes a value according to the provided schema.
   */
  public decode(data: Uint8Array, schema: XdrSchema): unknown {
    this.reader.reset(data);
    return this.readValue(schema);
  }
 
  /**
   * Reads a value according to its schema.
   */
  private readValue(schema: XdrSchema): unknown {
    switch (schema.type) {
      // Primitive types
      case 'void':
        return this.decoder.readVoid();
      case 'int':
        return this.decoder.readInt();
      case 'unsigned_int':
        return this.decoder.readUnsignedInt();
      case 'boolean':
        return this.decoder.readBoolean();
      case 'hyper':
        return this.decoder.readHyper();
      case 'unsigned_hyper':
        return this.decoder.readUnsignedHyper();
      case 'float':
        return this.decoder.readFloat();
      case 'double':
        return this.decoder.readDouble();
      case 'quadruple':
        return this.decoder.readQuadruple();
      case 'enum':
        return this.readEnum(schema as XdrEnumSchema);
 
      // Wide primitive types
      case 'opaque':
        return this.readOpaque(schema as XdrOpaqueSchema);
      case 'vopaque':
        return this.readVarlenOpaque(schema as XdrVarlenOpaqueSchema);
      case 'string':
        return this.readString(schema as XdrStringSchema);
 
      // Composite types
      case 'array':
        return this.readArray(schema as XdrArraySchema);
      case 'varray':
        return this.readVarlenArray(schema as XdrVarlenArraySchema);
      case 'struct':
        return this.readStruct(schema as XdrStructSchema);
      case 'union':
        return this.readUnion(schema as XdrUnionSchema);
      case 'optional':
        return this.readOptional(schema as XdrOptionalSchema);
      case 'const':
        // Constants are not decoded; they have no runtime representation
        return undefined;
 
      default:
        throw new Error(`Unknown schema type: ${(schema as any).type}`);
    }
  }
 
  /**
   * Reads an enum value according to the enum schema.
   */
  private readEnum(schema: XdrEnumSchema): string | number {
    const value = this.decoder.readEnum();
 
    // Find the enum name for this value
    for (const [name, enumValue] of Object.entries(schema.values)) {
      if (enumValue === value) {
        return name;
      }
    }
 
    // If no matching name found, return the numeric value
    return value;
  }
 
  /**
   * Reads opaque data according to the opaque schema.
   */
  private readOpaque(schema: XdrOpaqueSchema): Uint8Array {
    return this.decoder.readOpaque(schema.size);
  }
 
  /**
   * Reads variable-length opaque data according to the schema.
   */
  private readVarlenOpaque(schema: XdrVarlenOpaqueSchema): Uint8Array {
    const data = this.decoder.readVarlenOpaque();
 
    // Check size constraint if specified
    if (schema.size !== undefined && data.length > schema.size) {
      throw new Error(`Variable-length opaque data size ${data.length} exceeds maximum ${schema.size}`);
    }
 
    return data;
  }
 
  /**
   * Reads a string according to the string schema.
   */
  private readString(schema: XdrStringSchema): string {
    const str = this.decoder.readString();
 
    // Check size constraint if specified
    if (schema.size !== undefined && str.length > schema.size) {
      throw new Error(`String length ${str.length} exceeds maximum ${schema.size}`);
    }
 
    return str;
  }
 
  /**
   * Reads a fixed-size array according to the array schema.
   */
  private readArray(schema: XdrArraySchema): unknown[] {
    return this.decoder.readArray(schema.size, () => this.readValue(schema.elements));
  }
 
  /**
   * Reads a variable-length array according to the schema.
   */
  private readVarlenArray(schema: XdrVarlenArraySchema): unknown[] {
    const array = this.decoder.readVarlenArray(() => this.readValue(schema.elements));
 
    // Check size constraint if specified
    if (schema.size !== undefined && array.length > schema.size) {
      throw new Error(`Variable-length array size ${array.length} exceeds maximum ${schema.size}`);
    }
 
    return array;
  }
 
  /**
   * Reads a struct according to the struct schema.
   */
  private readStruct(schema: XdrStructSchema): Record<string, unknown> {
    const struct: Record<string, unknown> = {};
 
    for (const [fieldSchema, fieldName] of schema.fields) {
      struct[fieldName] = this.readValue(fieldSchema);
    }
 
    return struct;
  }
 
  /**
   * Reads a union according to the union schema.
   */
  private readUnion(schema: XdrUnionSchema): XdrUnion {
    // Read discriminant
    const discriminant = this.decoder.readInt();
 
    // Find matching arm
    for (const [armDiscriminant, armSchema] of schema.arms) {
      if (armDiscriminant === discriminant) {
        const value = this.readValue(armSchema);
        return new XdrUnion(discriminant, value);
      }
    }
 
    // If no matching arm found, try default
    if (schema.default) {
      const value = this.readValue(schema.default);
      return new XdrUnion(discriminant, value);
    }
 
    throw new Error(`No matching union arm for discriminant: ${discriminant}`);
  }
 
  /**
   * Reads optional-data according to the optional schema (RFC 1832 Section 3.19).
   * Optional-data is syntactic sugar for a union with boolean discriminant.
   * Returns null if opted is FALSE, otherwise returns the decoded value.
   */
  private readOptional(schema: XdrOptionalSchema): unknown | null {
    const opted = this.decoder.readBoolean();
    Iif (!opted) return null;
    return this.readValue(schema.element);
  }
}