added support for STAC file extension

.codespellignore

@@ -0,0 +1 @@
+filetest

pystac/__init__.py

@@ -41,6 +41,7 @@ class STACError(Exception):
 import pystac.extensions.timestamps
 import pystac.extensions.version
 import pystac.extensions.view
+import pystac.extensions.file
 
 STAC_EXTENSIONS = extensions.base.RegisteredSTACExtensions([
     extensions.eo.EO_EXTENSION_DEFINITION, extensions.label.LABEL_EXTENSION_DEFINITION,
@@ -49,7 +50,8 @@ class STACError(Exception):
     extensions.sat.SAT_EXTENSION_DEFINITION, extensions.scientific.SCIENTIFIC_EXTENSION_DEFINITION,
     extensions.single_file_stac.SFS_EXTENSION_DEFINITION,
     extensions.timestamps.TIMESTAMPS_EXTENSION_DEFINITION,
-    extensions.version.VERSION_EXTENSION_DEFINITION, extensions.view.VIEW_EXTENSION_DEFINITION
+    extensions.version.VERSION_EXTENSION_DEFINITION, extensions.view.VIEW_EXTENSION_DEFINITION,
+    extensions.file.FILE_EXTENSION_DEFINITION
 ])
 
 

pystac/extensions/__init__.py

@@ -29,3 +29,4 @@ def __str__(self):
     TIMESTAMPS = 'timestamps'
     VERSION = 'version'
     VIEW = 'view'
+    FILE = 'file'

pystac/extensions/file.py

@@ -0,0 +1,227 @@
+import enum
+
+from pystac import Extensions
+from pystac.item import Item
+from pystac.extensions.base import (ItemExtension, ExtensionDefinition, ExtendedObject)
+
+
+class FileDataType(enum.Enum):
+    INT8 = "int8"
+    INT16 = "int16"
+    INT32 = "int32"
+    INT64 = "int64"
+    UINT8 = "uint8"
+    UINT16 = "uint16"
+    UINT32 = "uint32"
+    UINT64 = "uint64"
+    FLOAT16 = "float16"
+    FLOAT32 = "float32"
+    FLOAT64 = "float64"
+    CINT16 = "cint16"
+    CINT32 = "cint32"
+    CFLOAT32 = "cfloat32"
+    CFLOAT64 = "cfloat64"
+    OTHER = "other"
+
+
+class FileItemExt(ItemExtension):
+    """FileItemExt is the extension of the Item in the file extension which
+    adds file related details such as checksum, data type and size for assets.
+
+    Args:
+        item (Item): The item to be extended.
+
+    Attributes:
+        item (Item): The Item that is being extended.
+
+    Note:
+        Using FileItemExt to directly wrap an item will add the 'file' extension ID to
+        the item's stac_extensions.
+    """
+    def __init__(self, item):
+        if item.stac_extensions is None:
+            item.stac_extensions = [Extensions.FILE]
+        elif Extensions.FILE not in item.stac_extensions:
+            item.stac_extensions.append(Extensions.FILE)
+
+        self.item = item
+
+    def apply(self, data_type=None, size=None, nodata=None, checksum=None):
+        """Applies file extension properties to the extended Item.
+
+        Args:
+            data_type (FileDataType): The data type of the file.
+            size (int or None): size of the file in bytes.
+            nodata (List[Object] or None): Value(s) for no-data.
+            checksum (str or None): Multihash for the corresponding file,
+                encoded as hexadecimal (base 16) string with lowercase letters.
+        """
+        self.data_type = data_type
+        self.size = size
+        self.nodata = nodata
+        self.checksum = checksum
+
+    def _set_property(self, key, value, asset):
+        target = self.item.properties if asset is None else asset.properties
+        if value is None:
+            target.pop(key, None)
+        else:
+            target[key] = value
+
+    @property
+    def data_type(self):
+        """Get or sets the data_type of the file.
+
+        Returns:
+            FileDataType
+        """
+        return self.get_data_type()
+
+    @data_type.setter
+    def data_type(self, v):
+        self.set_data_type(v)
+
+    def get_data_type(self, asset=None):
+        """Gets an Item or an Asset data_type.
+
+        If an Asset is supplied and the data_type property exists on the Asset,
+        returns the Asset's value. Otherwise returns the Item's value
+
+        Returns:
+            FileDataType
+        """
+        if asset is not None and 'file:data_type' in asset.properties:
+            data_type = asset.properties.get('file:data_type')
+        else:
+            data_type = self.item.properties.get('file:data_type')
+
+        if data_type is not None:
+            return FileDataType(data_type)
+
+    def set_data_type(self, data_type, asset=None):
+        """Set an Item or an Asset data_type.
+
+        If an Asset is supplied, sets the property on the Asset.
+        Otherwise sets the Item's value.
+        """
+        self._set_property('file:data_type', data_type.value, asset)
+
+    @property
+    def size(self):
+        """Get or sets the size in bytes of the file
+
+        Returns:
+            int or None
+        """
+        return self.get_size()
+
+    @size.setter
+    def size(self, v):
+        self.set_size(v)
+
+    def get_size(self, asset=None):
+        """Gets an Item or an Asset file size.
+
+        If an Asset is supplied and the Item property exists on the Asset,
+        returns the Asset's value. Otherwise returns the Item's value
+
+        Returns:
+            float
+        """
+        if asset is None or 'file:size' not in asset.properties:
+            return self.item.properties.get('file:size')
+        else:
+            return asset.properties.get('file:size')
+
+    def set_size(self, size, asset=None):
+        """Set an Item or an Asset size.
+
+        If an Asset is supplied, sets the property on the Asset.
+        Otherwise sets the Item's value.
+        """
+        self._set_property('file:size', size, asset)
+
+    @property
+    def nodata(self):
+        """Get or sets the no data values
+
+        Returns:
+            int or None
+        """
+        return self.get_nodata()
+
+    @nodata.setter
+    def nodata(self, v):
+        self.set_nodata(v)
+
+    def get_nodata(self, asset=None):
+        """Gets an Item or an Asset nodata values.
+
+        If an Asset is supplied and the Item property exists on the Asset,
+        returns the Asset's value. Otherwise returns the Item's value
+
+        Returns:
+            list[object]
+        """
+        if asset is None or 'file:nodata' not in asset.properties:
+            return self.item.properties.get('file:nodata')
+        else:
+            return asset.properties.get('file:nodata')
+
+    def set_nodata(self, nodata, asset=None):
+        """Set an Item or an Asset nodata values.
+
+        If an Asset is supplied, sets the property on the Asset.
+        Otherwise sets the Item's value.
+        """
+        self._set_property('file:nodata', nodata, asset)
+
+    @property
+    def checksum(self):
+        """Get or sets the checksum
+
+        Returns:
+            str or None
+        """
+        return self.get_checksum()
+
+    @checksum.setter
+    def checksum(self, v):
+        self.set_checksum(v)
+
+    def get_checksum(self, asset=None):
+        """Gets an Item or an Asset checksum.
+
+        If an Asset is supplied and the Item property exists on the Asset,
+        returns the Asset's value. Otherwise returns the Item's value
+
+        Returns:
+            list[object]
+        """
+        if asset is None or 'file:checksum' not in asset.properties:
+            return self.item.properties.get('file:checksum')
+        else:
+            return asset.properties.get('file:checksum')
+
+    def set_checksum(self, checksum, asset=None):
+        """Set an Item or an Asset checksum.
+
+        If an Asset is supplied, sets the property on the Asset.
+        Otherwise sets the Item's value.
+        """
+        self._set_property('file:checksum', checksum, asset)
+
+    def __repr__(self):
+        return '<FileItemExt Item id={}>'.format(self.item.id)
+
+    @classmethod
+    def _object_links(cls):
+        return []
+
+    @classmethod
+    def from_item(cls, item):
+        return cls(item)
+
+
+FILE_EXTENSION_DEFINITION = ExtensionDefinition(Extensions.FILE,
+                                                [ExtendedObject(Item, FileItemExt)])

tests/data-files/file/file-example.json

@@ -0,0 +1,100 @@
+{
+  "id": "S1A_EW_GRDM_1SSH_20181103T235855_20181103T235955_024430_02AD5D_5616",
+  "type": "Feature",
+  "stac_version": "1.0.0-beta.2",
+  "stac_extensions": [
+    "file"
+  ],
+  "bbox": [
+    -70.275032,
+    -64.72924,
+    -65.087479,
+    -51.105831
+  ],
+  "geometry": {
+    "type": "Polygon",
+    "coordinates": [
+      [
+        [
+          -67.071648,
+          -64.72924
+        ],
+        [
+          -65.087479,
+          -56.674374
+        ],
+        [
+          -68.033211,
+          -51.105831
+        ],
+        [
+          -70.275032,
+          -59.805672
+        ],
+        [
+          -67.071648,
+          -64.72924
+        ]
+      ]
+    ]
+  },
+  "properties": {
+    "datetime": "2018-11-03T23:58:55Z"
+  },
+  "assets": {
+    "noises": {
+      "href": "./annotation/calibration/noise-s1a-ew-grd-hh-20181103t235855-20181103t235955-024430-02ad5d-001.xml",
+      "title": "Calibration Schema",
+      "type": "text/xml",
+      "file:checksum": "90e40210a30d1711e81a4b11ef67b28744321659"
+    },
+    "calibrations": {
+      "href": "./annotation/calibration/calibration-s1a-ew-grd-hh-20181103t235855-20181103t235955-024430-02ad5d-001.xml",
+      "title": "Noise Schema",
+      "type": "text/xml",
+      "file:checksum": "90e402104fc5351af67db0b8f1746efe421a05e4"
+    },
+    "products": {
+      "href": "./annotation/s1a-ew-grd-hh-20181103t235855-20181103t235955-024430-02ad5d-001.xml",
+      "title": "Product Schema",
+      "type": "text/xml",
+      "file:checksum": "90e402107a7f2588a85362b9beea2a12d4514d45"
+    },
+    "measurement": {
+      "href": "./measurement/s1a-ew-grd-hh-20181103t235855-20181103t235955-024430-02ad5d-001.tiff",
+      "title": "Measurements",
+      "type": "image/tiff",
+      "file:byte_order": "little-endian",
+      "file:data_type": "uint16",
+      "file:size": 209715200,
+      "file:header_size": 4096,
+      "file:checksum": "90e40210163700a8a6501eccd00b6d3b44ddaed0"
+    },
+    "thumbnail": {
+      "href": "./preview/quick-look.png",
+      "title": "Thumbnail",
+      "type": "image/png",
+      "file:byte_order": "big-endian",
+      "file:data_type": "uint8",
+      "file:size": 146484,
+      "file:checksum": "90e40210f52acd32b09769d3b1871b420789456c",
+      "file:nodata": []
+    }
+  },
+  "links": [
+    {
+      "rel": "self",
+      "href": "https://example.com/collections/sentinel-1/items/S1A_EW_GRDM_1SSH_20181103T235855_20181103T235955_024430_02AD5D_5616"
+    },
+    {
+      "rel": "parent",
+      "href": "https://example.com/collections/sentinel-1",
+      "file:checksum": "11146d97123fd2c02dec9a1b6d3b13136dbe600cf966"
+    },
+    {
+      "rel": "root",
+      "href": "https://example.com/collections",
+      "file:checksum": "1114fa4b9d69fdddc7c1be7bed9440621400b383b43f"
+    }
+  ]
+}