common: introduce common conversion functions

Author: Kamil Vojanec

lbr_testsuite/common/__init__.py

@@ -5,10 +5,14 @@
     local_tests,
     wait_until_condition,
 )
+from .conv import mbps_to_mpps, mpps_to_mbps, parse_size
 from .sysctl import sysctl_get, sysctl_set, sysctl_set_with_restore
 
 
 __all__ = [
+    "mbps_to_mpps",
+    "mpps_to_mbps",
+    "parse_size",
     "sysctl_set",
     "sysctl_get",
     "sysctl_set_with_restore",

lbr_testsuite/common/conv.py

@@ -0,0 +1,120 @@
+"""
+Author(s): Kamil Vojanec <[email protected]>
+
+Copyright: (C) 2024 CESNET, z.s.p.o.
+
+Common conversion functions.
+"""
+
+import re
+from enum import StrEnum
+
+
+"""
+Extra bytes added to L2 packet size when converting:
+7B preamble + 1B SoF + 4B CRC + 12B minimal IFG.
+"""
+PACKET_EXTRA_BYTES = 24
+
+
+def mbps_to_mpps(thrpt_mbps: float, pkt_len: int):
+    """Convert megabits per second throughput into megapackets per second.
+
+    Parameters
+    ----------
+    thrpt_mbps : float
+        Throughput value in megabits per second (on L1).
+    pkt_len : int
+        Individual packet length in bytes (on L2 without FCS).
+
+    Returns
+    -------
+    float
+        Throughput value in megapackets per second.
+    """
+
+    return thrpt_mbps / ((pkt_len + PACKET_EXTRA_BYTES) * 8)
+
+
+def mpps_to_mbps(thrpt_mpps: float, pkt_len: int):
+    """Convert megapackets per second throughput into megabits per second.
+
+    Parameters
+    ----------
+    thrpt_mpps : float
+        Throughput value in megapackets per second.
+    pkt_len : int
+        Individual packet length in bytes (on L2 without FCS).
+
+    Returns
+    -------
+    float
+        Throughput value in megabits per second (on L1).
+    """
+
+    return thrpt_mpps * ((pkt_len + PACKET_EXTRA_BYTES) * 8)
+
+
+class UnitsPolicy(StrEnum):
+    """Units policy to be used in size conversion.
+    Used to avoid confusion when comparing decimal and binary
+    size values.
+    """
+
+    """SI defines base 10 prefixes for conversion.
+    See: https://en.wikipedia.org/wiki/Metric_prefix#List_of_SI_prefixes
+    """
+    SI = "si"
+
+    """IEC Defines binary prefixes for conversion.
+    See: https://en.wikipedia.org/wiki/Binary_prefix#Prefixes
+    """
+    IEC = "iec"
+
+
+def parse_size(
+    size_str: str,
+    units: UnitsPolicy = UnitsPolicy.SI,
+) -> int:
+    """Parse size - value with k, M, G suffix into
+    an integer representing the size in bytes.
+
+    Parameters
+    ----------
+    size_str : str
+        Size string to be parsed. Contains a value
+        with a unit (k, M, G, T).
+    units : UnitsPolicy
+        Specify the unit used for conversion.
+
+    Returns
+    -------
+    int
+        Integer size in bytes.
+    """
+
+    # First match group matches the value.
+    # Second match group matches the unit.
+    reg = r"(\d+)\s*([kMGT])"
+    match = re.match(reg, size_str).groups()
+
+    assert len(match) == 2, "Must match only the value and unit"
+
+    mult_table = {
+        UnitsPolicy.SI: {
+            "k": 1e3,
+            "M": 1e6,
+            "G": 1e9,
+            "T": 1e12,
+        },
+        UnitsPolicy.IEC: {
+            "k": 2**10,
+            "M": 2**20,
+            "G": 2**30,
+            "T": 2**40,
+        },
+    }
+
+    val = int(match[0])
+    mult = mult_table[units][match[1]]
+    return val * mult