DO NOT MERGE: More robust parsing of NPT time ranges in RTSP.

Change-Id: If5a00f1e29dbc12956e1fb000dac859706d19791
related-to-bug: 3217210

media/libstagefright/rtsp/ASessionDescription.cpp

@@ -254,26 +254,12 @@ bool ASessionDescription::getDurationUs(int64_t *durationUs) const {
         return false;
     }
 
-    if (value == "npt=now-" || value == "npt=0-") {
-        return false;
-    }
-
     if (strncmp(value.c_str(), "npt=", 4)) {
         return false;
     }
 
-    const char *s = value.c_str() + 4;
-    char *end;
-    double from = strtod(s, &end);
-
-    if (end == s || *end != '-') {
-        return false;
-    }
-
-    s = end + 1;
-    double to = strtod(s, &end);
-
-    if (end == s || *end != '\0' || to < from) {
+    float from, to;
+    if (!parseNTPRange(value.c_str() + 4, &from, &to)) {
         return false;
     }
 
@@ -307,5 +293,39 @@ void ASessionDescription::ParseFormatDesc(
     }
 }
 
+// static
+bool ASessionDescription::parseNTPRange(
+        const char *s, float *npt1, float *npt2) {
+    if (s[0] == '-') {
+        return false;  // no start time available.
+    }
+
+    if (!strncmp("now", s, 3)) {
+        return false;  // no absolute start time available
+    }
+
+    char *end;
+    *npt1 = strtof(s, &end);
+
+    if (end == s || *end != '-') {
+        // Failed to parse float or trailing "dash".
+        return false;
+    }
+
+    s = end + 1;  // skip the dash.
+
+    if (!strncmp("now", s, 3)) {
+        return false;  // no absolute end time available
+    }
+
+    *npt2 = strtof(s, &end);
+
+    if (end == s || *end != '\0') {
+        return false;
+    }
+
+    return *npt2 > *npt1;
+}
+
 }  // namespace android
 

media/libstagefright/rtsp/ASessionDescription.h

@@ -55,6 +55,14 @@ struct ASessionDescription : public RefBase {
 
     bool findAttribute(size_t index, const char *key, AString *value) const;
 
+    // parses strings of the form
+    //   npt      := npt-time "-" npt-time? | "-" npt-time
+    //   npt-time := "now" | [0-9]+("." [0-9]*)?
+    //
+    // Returns true iff both "npt1" and "npt2" times were available,
+    // i.e. we have a fixed duration, otherwise this is live streaming.
+    static bool parseNTPRange(const char *s, float *npt1, float *npt2);
+
 protected:
     virtual ~ASessionDescription();
 

media/libstagefright/rtsp/MyHandler.h

@@ -938,13 +938,11 @@ struct MyHandler : public AHandler {
 
         AString val;
         CHECK(GetAttribute(range.c_str(), "npt", &val));
-        float npt1, npt2;
 
-        if (val == "now-" || val == "0-") {
+        float npt1, npt2;
+        if (!ASessionDescription::parseNTPRange(val.c_str(), &npt1, &npt2)) {
             // This is a live stream and therefore not seekable.
             return;
-        } else {
-            CHECK_EQ(sscanf(val.c_str(), "%f-%f", &npt1, &npt2), 2);
         }
 
         i = response->mHeaders.indexOfKey("rtp-info");