1 files changed, 30 insertions, 10 deletions
diff --git a/src/trace_processor/importers/json/json_utils.cc b/src/trace_processor/importers/json/json_utils.cc
index be9492b61..d2e1c1850 100644
--- a/src/trace_processor/importers/json/json_utils.cc
+++ b/src/trace_processor/importers/json/json_utils.cc
@@ -62,17 +62,37 @@ std::optional<int64_t> CoerceToTs(const std::string& s) {
   PERFETTO_DCHECK(IsJsonSupported());
 
 #if PERFETTO_BUILDFLAG(PERFETTO_TP_JSON)
-  size_t lhs_end = std::min<size_t>(s.find('.'), s.size());
-  size_t rhs_start = std::min<size_t>(lhs_end + 1, s.size());
-  std::optional<int64_t> lhs = base::StringToInt64(s.substr(0, lhs_end));
-  std::optional<double> rhs =
-      base::StringToDouble("0." + s.substr(rhs_start, std::string::npos));
-  if ((!lhs.has_value() && lhs_end > 0) ||
-      (!rhs.has_value() && rhs_start < s.size())) {
-    return std::nullopt;
+  // 's' is formatted as a JSON Number, in microseconds
+  // goal: reformat 's' to be as an int, in nanoseconds
+  std::string s_as_ns = s;
+
+  // detect and remove scientific notation's exponents
+  int32_t exp_shift = 0;
+  if (size_t exp_start = s.find_first_of("eE");
+      exp_start != std::string::npos) {
+    const std::string exp_s = s.substr(exp_start + 1, s.size());
+    const std::optional<int32_t> exp = base::StringToInt32(exp_s);
+    if (!exp.has_value()) {
+      return std::nullopt;
+    }
+    s_as_ns.erase(exp_start);
+    exp_shift = *exp;
   }
-  return lhs.value_or(0) * 1000 +
-         static_cast<int64_t>(rhs.value_or(0) * 1000.0);
+
+  // detect and remove decimal separator
+  size_t int_size = s_as_ns.size();
+  if (size_t frac_start = s.find('.'); frac_start != std::string::npos) {
+    s_as_ns.erase(frac_start, 1);
+    int_size = frac_start;
+  }
+
+  // expand or shrink to the new size
+  constexpr int us_to_ns_shift = 3;
+  const size_t s_as_ns_size = size_t(
+      std::max<ptrdiff_t>(1, ptrdiff_t(int_size) + exp_shift + us_to_ns_shift));
+  s_as_ns.resize(s_as_ns_size, '0');  // pads or truncates
+
+  return base::StringToInt64(s_as_ns);
 #else
   perfetto::base::ignore_result(s);
   return std::nullopt;